annotate runtime/doc/vim9class.txt @ 33678:7d9d2404a3d4 v9.0.2076

patch 9.0.2076: Vim9: No support for type aliases Commit: https://github.com/vim/vim/commit/ec3cebbd2b6b7583d2f683f5e66345163ec122aa Author: Yegappan Lakshmanan <yegappan@yahoo.com> Date: Fri Oct 27 19:35:26 2023 +0200 patch 9.0.2076: Vim9: No support for type aliases Problem: Vim9: No support for type aliases Solution: Implement :type command A type definition is giving a name to a type specification. This also known type alias. :type ListOfStrings = list<string> The type alias can be used wherever a built-in type can be used. The type alias name must start with an upper case character. closes: #13407 Signed-off-by: Christian Brabandt <cb@256bit.org> Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
author Christian Brabandt <cb@256bit.org>
date Fri, 27 Oct 2023 19:45:05 +0200
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children f126ffc85f7c
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1 *vim9class.txt* For Vim version 9.0. Last change: 2023 Sep 18
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4 VIM REFERENCE MANUAL by Bram Moolenaar
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5
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6
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7 NOTE - This is not finished yet, anything can still change! - NOTE
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8
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9
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10 Vim9 classes, objects, interfaces, types and enums.
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11
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12 1. Overview |Vim9-class-overview|
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13 2. A simple class |Vim9-simple-class|
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14 3. Class variables and methods |Vim9-class-member|
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15 4. Using an abstract class |Vim9-abstract-class|
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16 5. Using an interface |Vim9-using-interface|
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17 6. More class details |Vim9-class|
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18 7. Type definition |Vim9-type|
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19 8. Enum |Vim9-enum|
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20
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21 9. Rationale
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22 10. To be done later
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23
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24 ==============================================================================
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25
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26 1. Overview *Vim9-class-overview*
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27
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28 The fancy term is "object-oriented programming". You can find lots of study
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29 material on this subject. Here we document what |Vim9| script provides,
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30 assuming you know the basics already. Added are helpful hints about how to
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31 use this functionality effectively. Vim9 classes and objects cannot be used
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32 in legacy Vim scripts and legacy functions.
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33
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34 The basic item is an object:
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35 - An object stores state. It contains one or more variables that can each
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36 have a value.
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37 - An object provides functions that use and manipulate its state. These
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38 functions are invoked "on the object", which is what sets it apart from the
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39 traditional separation of data and code that manipulates the data.
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40 - An object has a well defined interface, with typed member variables and
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41 methods.
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42 - Objects are created from a class and all objects have the same interface.
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43 This does not change at runtime, it is not dynamic.
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44
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45 An object can only be created by a class. A class provides:
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46 - A new() method, the constructor, which returns an object for the class.
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47 This method is invoked on the class name: MyClass.new().
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48 - State shared by all objects of the class: class variables (class members).
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49 - A hierarchy of classes, with super-classes and sub-classes, inheritance.
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50
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51 An interface is used to specify properties of an object:
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52 - An object can declare several interfaces that it implements.
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53 - Different objects implementing the same interface can be used the same way.
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54
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55 The class hierarchy allows for single inheritance. Otherwise interfaces are
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56 to be used where needed.
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57
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58
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59 Class modeling ~
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60
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61 You can model classes any way you like. Keep in mind what you are building,
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62 don't try to model the real world. This can be confusing, especially because
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63 teachers use real-world objects to explain class relations and you might think
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64 your model should therefore reflect the real world. It doesn't! The model
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65 should match your purpose.
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66
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67 Keep in mind that composition (an object contains other objects) is often
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68 better than inheritance (an object extends another object). Don't waste time
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69 trying to find the optimal class model. Or waste time discussing whether a
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70 square is a rectangle or that a rectangle is a square. It doesn't matter.
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72
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73 ==============================================================================
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74
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75 2. A simple class *Vim9-simple-class*
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76
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77 Let's start with a simple example: a class that stores a text position (see
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78 below for how to do this more efficiently): >
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79
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80 class TextPosition
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81 this.lnum: number
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82 this.col: number
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83
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84 def new(lnum: number, col: number)
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85 this.lnum = lnum
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86 this.col = col
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87 enddef
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88
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89 def SetLnum(lnum: number)
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90 this.lnum = lnum
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91 enddef
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92
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93 def SetCol(col: number)
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94 this.col = col
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95 enddef
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96
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97 def SetPosition(lnum: number, col: number)
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98 this.lnum = lnum
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99 this.col = col
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100 enddef
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101 endclass
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102 < *object* *Object*
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103 You can create an object from this class with the new() method: >
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104
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105 var pos = TextPosition.new(1, 1)
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106
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107 The object variables "lnum" and "col" can be accessed directly: >
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108
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109 echo $'The text position is ({pos.lnum}, {pos.col})'
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110 < *E1317* *E1327*
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111 If you have been using other object-oriented languages you will notice that
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112 in Vim the object members are consistently referred to with the "this."
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113 prefix. This is different from languages like Java and TypeScript. The
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114 naming convention makes the object members easy to spot. Also, when a
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115 variable does not have the "this." prefix you know it is not an object
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116 variable.
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117
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118
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119 Object variable write access ~
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120
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121 Now try to change an object variable directly: >
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122
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123 pos.lnum = 9
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124 < *E1335*
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125 This will give you an error! That is because by default object variables can
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126 be read but not set. That's why the TextPosition class provides a method for
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127 it: >
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128
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129 pos.SetLnum(9)
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130
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131 Allowing to read but not set an object variable is the most common and safest
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132 way. Most often there is no problem using a value, while setting a value may
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133 have side effects that need to be taken care of. In this case, the SetLnum()
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134 method could check if the line number is valid and either give an error or use
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135 the closest valid value.
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136 *:public* *E1331*
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137 If you don't care about side effects and want to allow the object variable to
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138 be changed at any time, you can make it public: >
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139
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140 public this.lnum: number
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141 public this.col: number
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142
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143 Now you don't need the SetLnum(), SetCol() and SetPosition() methods, setting
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144 "pos.lnum" directly above will no longer give an error.
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145 *E1326*
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146 If you try to set an object variable that doesn't exist you get an error: >
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147 pos.other = 9
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148 < E1326: Member not found on object "TextPosition": other ~
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149
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150 *E1376*
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151 A object variable cannot be accessed using the class name.
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152
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153 Private variables ~
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154 *private-variable* *E1332* *E1333*
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155 On the other hand, if you do not want the object variables to be read directly,
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156 you can make them private. This is done by prefixing an underscore to the
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157 name: >
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158
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159 this._lnum: number
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160 this._col number
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161
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162 Now you need to provide methods to get the value of the private variables.
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163 These are commonly called getters. We recommend using a name that starts with
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164 "Get": >
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165
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166 def GetLnum(): number
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167 return this._lnum
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168 enddef
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169
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170 def GetCol() number
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171 return this._col
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172 enddef
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173
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174 This example isn't very useful, the variables might as well have been public.
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175 It does become useful if you check the value. For example, restrict the line
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176 number to the total number of lines: >
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177
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178 def GetLnum(): number
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179 if this._lnum > this._lineCount
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180 return this._lineCount
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181 endif
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182 return this._lnum
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183 enddef
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184 <
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185 Private methods ~
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186 *private-method* *E1366*
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187 If you want object methods to be accessible only from other methods of the
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188 same class and not used from outside the class, then you can make them
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189 private. This is done by prefixing the method name with an underscore: >
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190
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191 class SomeClass
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192 def _Foo(): number
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193 return 10
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194 enddef
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195 def Bar(): number
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196 return this._Foo()
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197 enddef
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198 endclass
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199 <
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200 Accessing a private method outside the class will result in an error (using
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201 the above class): >
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202
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203 var a = SomeClass.new()
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204 a._Foo()
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205 <
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206 Simplifying the new() method ~
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207 *new()* *constructor*
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208 Many constructors take values for the object variables. Thus you very often
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209 see this pattern: >
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210
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211 class SomeClass
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212 this.lnum: number
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213 this.col: number
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214
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215 def new(lnum: number, col: number)
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216 this.lnum = lnum
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217 this.col = col
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218 enddef
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219 endclass
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220 <
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221 *E1390*
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222 Not only is this text you need to write, it also has the type of each
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223 variables twice. Since this is so common a shorter way to write new() is
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224 provided: >
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225
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226 def new(this.lnum, this.col)
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227 enddef
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228
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229 The semantics are easy to understand: Providing the object variable name,
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230 including "this.", as the argument to new() means the value provided in the
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231 new() call is assigned to that object variable. This mechanism comes from the
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232 Dart language.
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233
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234 Putting together this way of using new() and making the variables public
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235 results in a much shorter class definition than what we started with: >
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236
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237 class TextPosition
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238 public this.lnum: number
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239 public this.col: number
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240
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241 def new(this.lnum, this.col)
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242 enddef
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243
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244 def SetPosition(lnum: number, col: number)
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245 this.lnum = lnum
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246 this.col = col
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247 enddef
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248 endclass
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249
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250 The sequence of constructing a new object is:
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251 1. Memory is allocated and cleared. All values are zero/false/empty.
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252 2. For each declared object variable that has an initializer, the expression
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253 is evaluated and assigned to the variable. This happens in the sequence
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254 the variables are declared in the class.
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255 3. Arguments in the new() method in the "this.name" form are assigned.
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256 4. The body of the new() method is executed.
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257
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258 If the class extends a parent class, the same thing happens. In the second
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259 step the object variables of the parent class are initialized first. There is
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260 no need to call "super()" or "new()" on the parent.
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261
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262 *E1365*
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263 When defining the new() method the return type should not be specified. It
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264 always returns an object of the class.
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265
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266 *E1386*
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267 When invoking an object method, the method name should be preceded by the
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268 object variable name. A object method cannot be invoked using the class
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269 name.
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270
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271 ==============================================================================
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272
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273 3. Class Variables and Methods *Vim9-class-member*
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274
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275 *:static* *E1337* *E1338* *E1368*
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276 Class members are declared with "static". They are used by the name without a
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277 prefix in the class where they are defined: >
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278
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279 class OtherThing
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280 this.size: number
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281 static totalSize: number
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282
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283 def new(this.size)
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284 totalSize += this.size
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285 enddef
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286 endclass
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287 < *E1340* *E1341*
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288 Since the name is used as-is, shadowing the name by a method argument name
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289 or local variable name is not allowed.
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290
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291 *E1374* *E1375* *E1384* *E1385*
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292 To access a class member outside of the class where it is defined, the class
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293 name prefix must be used. A class member cannot be accessed using an object.
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294
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295 Just like object members the access can be made private by using an underscore
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296 as the first character in the name, and it can be made public by prefixing
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297 "public": >
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298
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299 class OtherThing
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300 static total: number # anybody can read, only class can write
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301 static _sum: number # only class can read and write
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302 public static result: number # anybody can read and write
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303 endclass
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304 <
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305 *class-method*
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306 Class methods are also declared with "static". They can use the class
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307 variables but they have no access to the object variables, they cannot use the
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308 "this" keyword:
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309 >
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310 class OtherThing
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311 this.size: number
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312 static totalSize: number
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313
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314 # Clear the total size and return the value it had before.
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315 static def ClearTotalSize(): number
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316 var prev = totalSize
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317 totalSize = 0
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318 return prev
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319 enddef
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320 endclass
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321
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322 Inside the class the class method can be called by name directly, outside the
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323 class the class name must be prefixed: `OtherThing.ClearTotalSize()`. To use
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324 a super class method in a child class, the class name must be prefixed.
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325
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326 Just like object methods the access can be made private by using an underscore
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327 as the first character in the method name: >
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328
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329 class OtherThing
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330 static def _Foo()
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331 echo "Foo"
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332 enddef
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333 def Bar()
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334 _Foo()
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335 enddef
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336 endclass
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337 <
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338 *E1370*
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339 Note that constructors cannot be declared as "static", because they always
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340 are.
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341
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342 To access the class methods and class variables of a super class in an
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343 extended class, the class name prefix should be used just as from anywhere
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344 outside of the defining class: >
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345
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346 vim9script
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347 class Vehicle
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348 static nextID: number = 1000
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349 static def GetID(): number
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350 nextID += 1
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351 return nextID
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352 enddef
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353 endclass
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354 class Car extends Vehicle
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355 this.myID: number
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356 def new()
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357 this.myID = Vehicle.GetID()
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358 enddef
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359 endclass
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360 <
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361 Class variables and methods are not inherited by a child class. A child class
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362 can declare a static variable or a method with the same name as the one in the
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363 super class. Depending on the class where the member is used the
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364 corresponding class member will be used. The type of the class member in a
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365 child class can be different from that in the super class.
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366
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367 ==============================================================================
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368
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369 4. Using an abstract class *Vim9-abstract-class*
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370
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371 An abstract class forms the base for at least one sub-class. In the class
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372 model one often finds that a few classes have the same properties that can be
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373 shared, but a class with these properties does not have enough state to create
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374 an object from. A sub-class must extend the abstract class and add the
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375 missing state and/or methods before it can be used to create objects for.
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376
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377 For example, a Shape class could store a color and thickness. You cannot
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378 create a Shape object, it is missing the information about what kind of shape
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379 it is. The Shape class functions as the base for a Square and a Triangle
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380 class, for which objects can be created. Example: >
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381
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382 abstract class Shape
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383 this.color = Color.Black
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384 this.thickness = 10
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385 endclass
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386
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387 class Square extends Shape
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388 this.size: number
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389
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390 def new(this.size)
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391 enddef
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392 endclass
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393
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394 class Triangle extends Shape
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395 this.base: number
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396 this.height: number
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397
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398 def new(this.base, this.height)
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399 enddef
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400 endclass
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401 <
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402 An abstract class is defined the same way as a normal class, except that it
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403 does not have any new() method. *E1359*
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404
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405 *abstract-method* *E1371* *E1372*
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406 An abstract method can be defined in an abstract class by using the "abstract"
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407 prefix when defining the method: >
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408
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409 abstract class Shape
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410 abstract def Draw()
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411 abstract static def SetColor()
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412 endclass
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413 <
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414 *E1373*
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415 A class extending the abstract class must implement all the abstract methods.
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416 The signature (arguments, argument types and return type) must be exactly the
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417 same. If the return type of a method is a class, then that class or one of
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418 its subclasses can be used in the extended method. Class methods in an
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419 abstract class can also be abstract methods.
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420
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421 ==============================================================================
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422
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423 5. Using an interface *Vim9-using-interface*
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424
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425 The example above with Shape, Square and Triangle can be made more useful if
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426 we add a method to compute the surface of the object. For that we create the
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427 interface called HasSurface, which specifies one method Surface() that returns
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428 a number. This example extends the one above: >
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429
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430 abstract class Shape
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431 this.color = Color.Black
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432 this.thickness = 10
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433 endclass
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434
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435 interface HasSurface
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436 def Surface(): number
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437 endinterface
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438
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439 class Square extends Shape implements HasSurface
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440 this.size: number
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441
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442 def new(this.size)
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443 enddef
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444
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445 def Surface(): number
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446 return this.size * this.size
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447 enddef
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448 endclass
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449
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450 class Triangle extends Shape implements HasSurface
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451 this.base: number
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452 this.height: number
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453
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454 def new(this.base, this.height)
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455 enddef
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456
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457 def Surface(): number
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458 return this.base * this.height / 2
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459 enddef
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460 endclass
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461 <
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462 *E1348* *E1349* *E1367* *E1382* *E1383*
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463 If a class declares to implement an interface, all the items specified in the
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464 interface must appear in the class, with the same types.
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465
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466 The interface name can be used as a type: >
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467
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468 var shapes: list<HasSurface> = [
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469 Square.new(12),
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470 Triangle.new(8, 15),
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471 ]
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472 for shape in shapes
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473 echo $'the surface is {shape.Surface()}'
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474 endfor
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475 <
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476 *E1378* *E1379* *E1380* *E1387*
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diff changeset
477 An interface can contain only object methods and read-only object variables.
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478 An interface cannot contain read-write and private object variables, private
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479 object methods, class variables and class methods.
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480
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481 An interface can extend another interface using "extends". The sub-interface
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482 inherits all the instance variables and methods from the super interface.
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483
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484 ==============================================================================
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485
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486 6. More class details *Vim9-class* *Class* *class*
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diff changeset
487
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diff changeset
488 Defining a class ~
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489 *:class* *:endclass* *:abstract*
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490 A class is defined between `:class` and `:endclass`. The whole class is
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491 defined in one script file. It is not possible to add to a class later.
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492
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493 A class can only be defined in a |Vim9| script file. *E1316*
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494 A class cannot be defined inside a function.
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495
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496 It is possible to define more than one class in a script file. Although it
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497 usually is better to export only one main class. It can be useful to define
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498 types, enums and helper classes though.
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499
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500 The `:abstract` keyword may be prefixed and `:export` may be used. That gives
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diff changeset
501 these variants: >
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diff changeset
502
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diff changeset
503 class ClassName
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504 endclass
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505
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506 export class ClassName
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507 endclass
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diff changeset
508
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diff changeset
509 abstract class ClassName
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510 endclass
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diff changeset
511
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512 export abstract class ClassName
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513 endclass
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514 <
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515 *E1314*
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516 The class name should be CamelCased. It must start with an uppercase letter.
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517 That avoids clashing with builtin types.
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518 *E1315*
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519 After the class name these optional items can be used. Each can appear only
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520 once. They can appear in any order, although this order is recommended: >
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521 extends ClassName
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522 implements InterfaceName, OtherInterface
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523 specifies SomeInterface
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524 < *E1355* *E1369*
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525 Each variable and method name can be used only once. It is not possible to
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526 define a method with the same name and different type of arguments. It is not
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527 possible to use a public and private member variable with the same name. A
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diff changeset
528 object variable name used in a super class cannot be reused in a child class.
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Bram Moolenaar <Bram@vim.org>
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diff changeset
529
cc751d944b7e Update runtime files.
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parents: 31671
diff changeset
530
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
531 Object Variable Initialization ~
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
532 If the type of a variable is not explicitly specified in a class, then it is
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
533 set to "any" during class definition. When an object is instantiated from the
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
534 class, then the type of the variable is set.
32960
d5c05e15cf81 patch 9.0.1780: Vim9 type not defined during object creation
Christian Brabandt <cb@256bit.org>
parents: 32903
diff changeset
535
33401
bb99820510ef patch 9.0.1959: Vim9: methods parameters and types are covariant
Christian Brabandt <cb@256bit.org>
parents: 33385
diff changeset
536 The following reserved keyword names cannot be used as an object or class
bb99820510ef patch 9.0.1959: Vim9: methods parameters and types are covariant
Christian Brabandt <cb@256bit.org>
parents: 33385
diff changeset
537 variable name: "super", "this", "true", "false", "null", "null_blob",
bb99820510ef patch 9.0.1959: Vim9: methods parameters and types are covariant
Christian Brabandt <cb@256bit.org>
parents: 33385
diff changeset
538 "null_dict", "null_function", "null_list", "null_partial", "null_string",
bb99820510ef patch 9.0.1959: Vim9: methods parameters and types are covariant
Christian Brabandt <cb@256bit.org>
parents: 33385
diff changeset
539 "null_channel" and "null_job".
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Christian Brabandt <cb@256bit.org>
parents: 32903
diff changeset
540
31885
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
541 Extending a class ~
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
542 *extends*
31671
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Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
543 A class can extend one other class. *E1352* *E1353* *E1354*
31885
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
544 The basic idea is to build on top of an existing class, add properties to it.
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
545
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parents: 31671
diff changeset
546 The extended class is called the "base class" or "super class". The new class
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
547 is called the "child class".
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
548
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
549 Object variables from the base class are all taken over by the child class. It
31885
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
550 is not possible to override them (unlike some other languages).
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
551
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
552 *E1356* *E1357* *E1358*
33432
97ceabebaeaf patch 9.0.1974: vim9: using contra-variant type-checks
Christian Brabandt <cb@256bit.org>
parents: 33401
diff changeset
553 Object methods of the base class can be overruled. The signature (arguments,
33490
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
554 argument types and return type) must be exactly the same. If the return type
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
555 of a method is a class, then that class or one of its subclasses can be used
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
556 in the extended method. The method of the base class can be called by
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
557 prefixing "super.".
31885
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
558
33286
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Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
559 *E1377*
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
560 The access level of a method (public or private) in a child class should be
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
561 the same as the super class.
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
562
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
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diff changeset
563 Other object methods of the base class are taken over by the child class.
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
564
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
565 Class methods, including methods starting with "new", can be overruled, like
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
566 with object methods. The method on the base class can be called by prefixing
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
567 the name of the class (for class methods) or "super.".
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
568
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
569 Unlike other languages, the constructor of the base class does not need to be
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
570 invoked. In fact, it cannot be invoked. If some initialization from the base
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
571 class also needs to be done in a child class, put it in an object method and
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
572 call that method from every constructor().
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
573
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
574 If the base class did not specify a new() method then one was automatically
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
575 created. This method will not be taken over by the child class. The child
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
576 class can define its own new() method, or, if there isn't one, a new() method
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
577 will be added automatically.
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
578
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Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
579
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
580 A class implementing an interface ~
33372
3e9a91624b40 patch 9.0.1945: Vim9: missing support for ro-vars in interface
Christian Brabandt <cb@256bit.org>
parents: 33351
diff changeset
581 *implements* *E1346* *E1347* *E1389*
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5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
582 A class can implement one or more interfaces. The "implements" keyword can
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
583 only appear once *E1350* . Multiple interfaces can be specified, separated by
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
584 commas. Each interface name can appear only once. *E1351*
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
585
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
586
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
587 A class defining an interface ~
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
588 *specifies*
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
589 A class can declare its interface, the object variables and methods, with a
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
590 named interface. This avoids the need for separately specifying the
31396
307f68a41b03 patch 9.0.1031: Vim9 class is not implemented yet
Bram Moolenaar <Bram@vim.org>
parents: 31335
diff changeset
591 interface, which is often done in many languages, especially Java.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
592
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
593
31430
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Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
594 Items in a class ~
33372
3e9a91624b40 patch 9.0.1945: Vim9: missing support for ro-vars in interface
Christian Brabandt <cb@256bit.org>
parents: 33351
diff changeset
595 *E1318* *E1325* *E1388*
32061
b2412874362f Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 32004
diff changeset
596 Inside a class, in between `:class` and `:endclass`, these items can appear:
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
597 - An object variable declaration: >
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
598 this._privateVariableName: memberType
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
599 this.readonlyVariableName: memberType
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
600 public this.readwriteVariableName: memberType
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
601 - A class variable declaration: >
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
602 static _privateClassVariableName: memberType
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
603 static readonlyClassVariableName: memberType
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
604 static public readwriteClassVariableName: memberType
31430
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Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
605 - A constructor method: >
32004
a9b5ffbc0428 Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
606 def new(arguments)
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Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
607 def newName(arguments)
33286
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
608 - A class method: >
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
609 static def SomeMethod(arguments)
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
610 static def _PrivateMethod(arguments)
31430
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Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
611 - An object method: >
32004
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Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
612 def SomeMethod(arguments)
33286
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
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diff changeset
613 def _PrivateMethod(arguments)
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
614
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
615 For the object variable the type must be specified. The best way is to do
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
616 this explicitly with ": {type}". For simple types you can also use an
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
617 initializer, such as "= 123", and Vim will see that the type is a number.
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
618 Avoid doing this for more complex types and when the type will be incomplete.
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
619 For example: >
31579
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Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
620 this.nameList = []
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Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
621 This specifies a list, but the item type is unknown. Better use: >
7d68a90cbf5c Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
622 this.nameList: list<string>
7d68a90cbf5c Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
623 The initialization isn't needed, the list is empty by default.
7d68a90cbf5c Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
624 *E1330*
7d68a90cbf5c Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31441
diff changeset
625 Some types cannot be used, such as "void", "null" and "v:none".
31430
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parents: 31396
diff changeset
626
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
627
31335
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Bram Moolenaar <Bram@vim.org>
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diff changeset
628 Defining an interface ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
629 *:interface* *:endinterface*
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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diff changeset
630 An interface is defined between `:interface` and `:endinterface`. It may be
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
631 prefixed with `:export`: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
632
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
633 interface InterfaceName
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
634 endinterface
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
635
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
636 export interface InterfaceName
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
637 endinterface
31671
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Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
638 < *E1344*
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
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diff changeset
639 An interface can declare object variables, just like in a class but without
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
640 any initializer.
31671
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
641 *E1345*
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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parents:
diff changeset
642 An interface can declare methods with `:def`, including the arguments and
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
643 return type, but without the body and without `:enddef`. Example: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
644
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
645 interface HasSurface
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
646 this.size: number
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
647 def Surface(): number
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
648 endinterface
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
649
31671
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parents: 31579
diff changeset
650 An interface name must start with an uppercase letter. *E1343*
31335
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
651 The "Has" prefix can be used to make it easier to guess this is an interface
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
652 name, with a hint about what it provides.
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
653 An interface can only be defined in a |Vim9| script file. *E1342*
33286
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Christian Brabandt <cb@256bit.org>
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diff changeset
654 An interface cannot "implement" another interface but it can "extend" another
0c3553cfe22e patch 9.0.1909: Vim9: problem calling class method from other class
Christian Brabandt <cb@256bit.org>
parents: 33217
diff changeset
655 interface. *E1381*
31335
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parents:
diff changeset
656
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
657
32004
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Bram Moolenaar <Bram@vim.org>
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diff changeset
658 null object ~
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Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
659
32061
b2412874362f Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 32004
diff changeset
660 When a variable is declared to have the type of an object, but it is not
32004
a9b5ffbc0428 Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
661 initialized, the value is null. When trying to use this null object Vim often
a9b5ffbc0428 Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
662 does not know what class was supposed to be used. Vim then cannot check if
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
663 a variable name is correct and you will get an "Using a null object" error,
33434
484543479bd7 runtime(doc): fix typos.
Christian Brabandt <cb@256bit.org>
parents: 33432
diff changeset
664 even when the variable name is invalid. *E1360* *E1362*
32004
a9b5ffbc0428 Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
665
a9b5ffbc0428 Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31885
diff changeset
666
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
667 Default constructor ~
33383
5c12ca4dcd45 patch 9.0.1950: Vim9: error codes spread out
Christian Brabandt <cb@256bit.org>
parents: 33379
diff changeset
668 *default-constructor*
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
669 In case you define a class without a new() method, one will be automatically
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
670 defined. This default constructor will have arguments for all the object
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
671 variables, in the order they were specified. Thus if your class looks like: >
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
672
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
673 class AutoNew
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
674 this.name: string
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
675 this.age: number
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
676 this.gender: Gender
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
677 endclass
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
678
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
679 Then the default constructor will be: >
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
680
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
681 def new(this.name = v:none, this.age = v:none, this.gender = v:none)
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
682 enddef
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
683
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
684 The "= v:none" default values make the arguments optional. Thus you can also
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
685 call `new()` without any arguments. No assignment will happen and the default
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
686 value for the object variables will be used. This is a more useful example,
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
687 with default values: >
31430
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
688
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
689 class TextPosition
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
690 this.lnum: number = 1
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
691 this.col: number = 1
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
692 endclass
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
693
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
694 If you want the constructor to have mandatory arguments, you need to write it
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
695 yourself. For example, if for the AutoNew class above you insist on getting
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
696 the name, you can define the constructor like this: >
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
697
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
698 def new(this.name, this.age = v:none, this.gender = v:none)
31430
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
699 enddef
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
700 < *E1328*
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
701 Note that you cannot use another default value than "v:none" here. If you
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
702 want to initialize the object variables, do it where they are declared. This
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
703 way you only need to look in one place for the default values.
31430
e5e95e8c78a7 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
704
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
705 All object variables will be used in the default constructor, also private
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
706 access ones.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
707
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
708 If the class extends another one, the object variables of that class will come
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
709 first.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
710
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
711
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
712 Multiple constructors ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
713
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
714 Normally a class has just one new() constructor. In case you find that the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
715 constructor is often called with the same arguments you may want to simplify
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
716 your code by putting those arguments into a second constructor method. For
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
717 example, if you tend to use the color black a lot: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
718
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
719 def new(this.garment, this.color, this.size)
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
720 enddef
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
721 ...
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
722 var pants = new(Garment.pants, Color.black, "XL")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
723 var shirt = new(Garment.shirt, Color.black, "XL")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
724 var shoes = new(Garment.shoes, Color.black, "45")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
725
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
726 Instead of repeating the color every time you can add a constructor that
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
727 includes it: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
728
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
729 def newBlack(this.garment, this.size)
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
730 this.color = Color.black
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
731 enddef
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
732 ...
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
733 var pants = newBlack(Garment.pants, "XL")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
734 var shirt = newBlack(Garment.shirt, "XL")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
735 var shoes = newBlack(Garment.shoes, "9.5")
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
736
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
737 Note that the method name must start with "new". If there is no method called
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
738 "new()" then the default constructor is added, even though there are other
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
739 constructor methods.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
740
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
741
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
742 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
743
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
744 7. Type definition *Vim9-type* *:type*
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
745
33678
7d9d2404a3d4 patch 9.0.2076: Vim9: No support for type aliases
Christian Brabandt <cb@256bit.org>
parents: 33636
diff changeset
746 A type definition is giving a name to a type specification. This also known
7d9d2404a3d4 patch 9.0.2076: Vim9: No support for type aliases
Christian Brabandt <cb@256bit.org>
parents: 33636
diff changeset
747 type alias. For Example: >
33490
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
748
33678
7d9d2404a3d4 patch 9.0.2076: Vim9: No support for type aliases
Christian Brabandt <cb@256bit.org>
parents: 33636
diff changeset
749 :type ListOfStrings = list<string>
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
750
33678
7d9d2404a3d4 patch 9.0.2076: Vim9: No support for type aliases
Christian Brabandt <cb@256bit.org>
parents: 33636
diff changeset
751 The type alias can be used wherever a built-in type can be used. The type
7d9d2404a3d4 patch 9.0.2076: Vim9: No support for type aliases
Christian Brabandt <cb@256bit.org>
parents: 33636
diff changeset
752 alias name must start with an upper case character.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
753
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
754 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
755
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
756 8. Enum *Vim9-enum* *:enum* *:endenum*
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
757
33490
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
758 {not implemented yet}
33593174288b runtime(doc): Update vim9class help (#13292)
Christian Brabandt <cb@256bit.org>
parents: 33434
diff changeset
759
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
760 An enum is a type that can have one of a list of values. Example: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
761
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
762 :enum Color
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
763 White
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
764 Red
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
765 Green
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
766 Blue
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
767 Black
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
768 :endenum
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
769
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
770
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
771 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
772
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
773 9. Rationale
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
774
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
775 Most of the choices for |Vim9| classes come from popular and recently
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
776 developed languages, such as Java, TypeScript and Dart. The syntax has been
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
777 made to fit with the way Vim script works, such as using `endclass` instead of
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
778 using curly braces around the whole class.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
779
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
780 Some common constructs of object-oriented languages were chosen very long ago
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
781 when this kind of programming was still new, and later found to be
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
782 sub-optimal. By this time those constructs were widely used and changing them
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
783 was not an option. In Vim we do have the freedom to make different choices,
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
784 since classes are completely new. We can make the syntax simpler and more
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
785 consistent than what "old" languages use. Without diverting too much, it
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
786 should still mostly look like what you know from existing languages.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
787
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
788 Some recently developed languages add all kinds of fancy features that we
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
789 don't need for Vim. But some have nice ideas that we do want to use.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
790 Thus we end up with a base of what is common in popular languages, dropping
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
791 what looks like a bad idea, and adding some nice features that are easy to
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
792 understand.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
793
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
794 The main rules we use to make decisions:
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
795 - Keep it simple.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
796 - No surprises, mostly do what other languages are doing.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
797 - Avoid mistakes from the past.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
798 - Avoid the need for the script writer to consult the help to understand how
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
799 things work, most things should be obvious.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
800 - Keep it consistent.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
801 - Aim at an average size plugin, not at a huge project.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
802
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
803
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
804 Using new() for the constructor ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
805
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
806 Many languages use the class name for the constructor method. A disadvantage
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
807 is that quite often this is a long name. And when changing the class name all
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
808 constructor methods need to be renamed. Not a big deal, but still a
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
809 disadvantage.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
810
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
811 Other languages, such as TypeScript, use a specific name, such as
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
812 "constructor()". That seems better. However, using "new" or "new()" to
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
813 create a new object has no obvious relation with "constructor()".
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
814
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
815 For |Vim9| script using the same method name for all constructors seemed like
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
816 the right choice, and by calling it new() the relation between the caller and
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
817 the method being called is obvious.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
818
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
819
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
820 No overloading of the constructor ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
821
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
822 In Vim script, both legacy and |Vim9| script, there is no overloading of
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
823 methods. That means it is not possible to use the same method name with
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
824 different types of arguments. Therefore there also is only one new()
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
825 constructor.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
826
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
827 With |Vim9| script it would be possible to support overloading, since
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
828 arguments are typed. However, this gets complicated very quickly. Looking at
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
829 a new() call one has to inspect the types of the arguments to know which of
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
830 several new() methods is actually being called. And that can require
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
831 inspecting quite a bit of code. For example, if one of the arguments is the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
832 return value of a method, you need to find that method to see what type it is
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
833 returning.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
834
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
835 Instead, every constructor has to have a different name, starting with "new".
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
836 That way multiple constructors with different arguments are possible, while it
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
837 is very easy to see which constructor is being used. And the type of
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
838 arguments can be properly checked.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
839
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
840
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
841 No overloading of methods ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
842
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
843 Same reasoning as for the constructor: It is often not obvious what type
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
844 arguments have, which would make it difficult to figure out what method is
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
845 actually being called. Better just give the methods a different name, then
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
846 type checking will make sure it works as you intended. This rules out
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
847 polymorphism, which we don't really need anyway.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
848
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
849
31671
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parents: 31579
diff changeset
850 Single inheritance and interfaces ~
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
851
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
852 Some languages support multiple inheritance. Although that can be useful in
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
853 some cases, it makes the rules of how a class works quite complicated.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
854 Instead, using interfaces to declare what is supported is much simpler. The
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
855 very popular Java language does it this way, and it should be good enough for
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
856 Vim. The "keep it simple" rule applies here.
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
857
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
858 Explicitly declaring that a class supports an interface makes it easy to see
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
859 what a class is intended for. It also makes it possible to do proper type
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
860 checking. When an interface is changed any class that declares to implement
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
861 it will be checked if that change was also changed. The mechanism to assume a
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
862 class implements an interface just because the methods happen to match is
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
863 brittle and leads to obscure problems, let's not do that.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
864
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
865
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
866 Using "this.variable" everywhere ~
31335
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
867
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
868 The object variables in various programming languages can often be accessed in
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
869 different ways, depending on the location. Sometimes "this." has to be
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
870 prepended to avoid ambiguity. They are usually declared without "this.".
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
871 That is quite inconsistent and sometimes confusing.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
872
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
873 A very common issue is that in the constructor the arguments use the same name
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
874 as the object variable. Then for these variables "this." needs to be prefixed
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
875 in the body, while for other variables this is not needed and often omitted.
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
876 This leads to a mix of variables with and without "this.", which is
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
877 inconsistent.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
878
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
879 For |Vim9| classes the "this." prefix is always used. Also for declaring the
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
880 variables. Simple and consistent. When looking at the code inside a class
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
881 it's also directly clear which variable references are object variables and
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
882 which aren't.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
883
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
884
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
885 Using class variables ~
31335
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
886
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
887 Using "static variable" to declare a class variable is very common, nothing
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
888 new here. In |Vim9| script these can be accessed directly by their name.
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
889 Very much like how a script-local variable can be used in a method. Since
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
890 object variables are always accessed with "this." prepended, it's also quickly
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
891 clear what kind of variable it is.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
892
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
893 TypeScript prepends the class name before the class variable name, also inside
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
894 the class. This has two problems: The class name can be rather long, taking
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
895 up quite a bit of space, and when the class is renamed all these places need
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
896 to be changed too.
31335
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
897
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
898
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
899 Declaring object and class variables ~
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
900
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
901 The main choice is whether to use "var" as with variable declarations.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
902 TypeScript does not use it: >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
903 class Point {
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parents: 31579
diff changeset
904 x: number;
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Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
905 y = 0;
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
906 }
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parents: 31579
diff changeset
907
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
908 Following that Vim object variables could be declared like this: >
31671
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parents: 31579
diff changeset
909 class Point
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parents: 31579
diff changeset
910 this.x: number
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parents: 31579
diff changeset
911 this.y = 0
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parents: 31579
diff changeset
912 endclass
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parents: 31579
diff changeset
913
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parents: 31579
diff changeset
914 Some users pointed out that this looks more like an assignment than a
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
915 declaration. Adding "var" changes that: >
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parents: 31579
diff changeset
916 class Point
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parents: 31579
diff changeset
917 var this.x: number
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diff changeset
918 var this.y = 0
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919 endclass
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920
33351
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Christian Brabandt <cb@256bit.org>
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diff changeset
921 We also need to be able to declare class variables using the "static" keyword.
31671
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Bram Moolenaar <Bram@vim.org>
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diff changeset
922 There we can also choose to leave out "var": >
5ed19049b1e8 Update runtime files
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parents: 31579
diff changeset
923 class Point
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Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
924 var this.x: number
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parents: 31579
diff changeset
925 static count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
926 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
927
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
928 Or do use it, before "static": >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
929 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
930 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
931 var static count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
932 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
933
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
934 Or after "static": >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
935 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
936 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
937 static var count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
938 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
939
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
940 This is more in line with "static def Func()".
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
941
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
942 There is no clear preference whether to use "var" or not. The two main
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
943 reasons to leave it out are:
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
944 1. TypeScript, Java and other popular languages do not use it.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
945 2. Less clutter.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
946
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
947
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
948 Using "ClassName.new()" to construct an object ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
949
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
950 Many languages use the "new" operator to create an object, which is actually
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
951 kind of strange, since the constructor is defined as a method with arguments,
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
952 not a command. TypeScript also has the "new" keyword, but the method is
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
953 called "constructor()", it is hard to see the relation between the two.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
954
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
955 In |Vim9| script the constructor method is called new(), and it is invoked as
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
956 new(), simple and straightforward. Other languages use "new ClassName()",
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
957 while there is no ClassName() method, it's a method by another name in the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
958 class called ClassName. Quite confusing.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
959
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
960
33351
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Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
961 Default read access to object variables ~
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
962
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
963 Some users will remark that the access rules for object variables are
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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parents:
diff changeset
964 asymmetric. Well, that is intentional. Changing a value is a very different
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
965 action than reading a value. The read operation has no side effects, it can
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
966 be done any number of times without affecting the object. Changing the value
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
967 can have many side effects, and even have a ripple effect, affecting other
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
968 objects.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
969
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
970 When adding object variables one usually doesn't think much about this, just
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
971 get the type right. And normally the values are set in the new() method.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
972 Therefore defaulting to read access only "just works" in most cases. And when
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
973 directly writing you get an error, which makes you wonder if you actually want
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
974 to allow that. This helps writing code with fewer mistakes.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
975
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
976
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
977 Making object variables private with an underscore ~
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
978
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
979 When an object variable is private, it can only be read and changed inside the
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
980 class (and in sub-classes), then it cannot be used outside of the class.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
981 Prepending an underscore is a simple way to make that visible. Various
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
982 programming languages have this as a recommendation.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
983
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
984 In case you change your mind and want to make the object variable accessible
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
985 outside of the class, you will have to remove the underscore everywhere.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
986 Since the name only appears in the class (and sub-classes) they will be easy
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
987 to find and change.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
988
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
989 The other way around is much harder: you can easily prepend an underscore to
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
990 the object variable inside the class to make it private, but any usage
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
991 elsewhere you will have to track down and change. You may have to make it a
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
992 "set" method call. This reflects the real world problem that taking away
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
993 access requires work to be done for all places where that access exists.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
994
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
995 An alternative would have been using the "private" keyword, just like "public"
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
996 changes the access in the other direction. Well, that's just to reduce the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
997 number of keywords.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
998
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
999
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
1000 No protected object variables ~
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1001
33351
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
1002 Some languages provide several ways to control access to object variables.
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
1003 The most known is "protected", and the meaning varies from language to
a3bbd065fb87 runtime(doc): Vim9: Consistenly use class/object variable and class/object method in help (#13149)
Christian Brabandt <cb@256bit.org>
parents: 33286
diff changeset
1004 language. Others are "shared", "private" and even "friend".
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1005
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1006 These rules make life more difficult. That can be justified in projects where
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1007 many people work on the same, complex code where it is easy to make mistakes.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1008 Especially when refactoring or other changes to the class model.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1009
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1010 The Vim scripts are expected to be used in a plugin, with just one person or a
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1011 small team working on it. Complex rules then only make it more complicated,
32294
b2e8663e6dcc Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 32061
diff changeset
1012 the extra safety provided by the rules isn't really needed. Let's just keep
b2e8663e6dcc Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 32061
diff changeset
1013 it simple and not specify access details.
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1014
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1015
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1016 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1017
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1018 10. To be done later
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1019
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1020 Can a newSomething() constructor invoke another constructor? If yes, what are
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1021 the restrictions?
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1022
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1023 Thoughts:
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1024 - Generics for a class: `class <Tkey, Tentry>`
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1025 - Generics for a function: `def <Tkey> GetLast(key: Tkey)`
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1026 - Mixins: not sure if that is useful, leave out for simplicity.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1027
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1028 Some things that look like good additions:
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1029 - For testing: Mock mechanism
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1030
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1031 An important class to be provided is "Promise". Since Vim is single
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1032 threaded, connecting asynchronous operations is a natural way of allowing
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1033 plugins to do their work without blocking the user. It's a uniform way to
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1034 invoke callbacks and handle timeouts and errors.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1035
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1036
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
1037 vim:tw=78:ts=8:noet:ft=help:norl: