annotate runtime/doc/vim9class.txt @ 32061:b2412874362f

Update runtime files Commit: https://github.com/vim/vim/commit/dd60c365cd2630794be84d63c4fe287124a30b97 Author: Bram Moolenaar <Bram@vim.org> Date: Mon Feb 27 15:49:53 2023 +0000 Update runtime files
author Bram Moolenaar <Bram@vim.org>
date Mon, 27 Feb 2023 17:00:08 +0100
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1 *vim9class.txt* For Vim version 9.0. Last change: 2023 Feb 26
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3
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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 members and functions |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.
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32
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33 The basic item is an object:
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34 - An object stores state. It contains one or more variables that can each
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35 have a value.
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36 - An object provides functions that use and manipulate its state. These
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37 functions are invoked "on the object", which is what sets it apart from the
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38 traditional separation of data and code that manipulates the data.
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39 - An object has a well defined interface, with typed member variables and
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40 member functions.
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41 - Objects are created from a class and all objects have the same interface.
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42 This does not change at runtime, it is not dynamic.
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43
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44 An object can only be created by a class. A class provides:
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45 - A new() method, the constructor, which returns an object for the class.
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46 This method is invoked on the class name: MyClass.new().
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47 - State shared by all objects of the class: class variables (class members).
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48 - A hierarchy of classes, with super-classes and sub-classes, inheritance.
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49
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50 An interface is used to specify properties of an object:
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51 - An object can declare several interfaces that it implements.
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52 - Different objects implementing the same interface can be used the same way.
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53
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54 The class hierarchy allows for single inheritance. Otherwise interfaces are
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55 to be used where needed.
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56
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57
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58 Class modeling ~
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59
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60 You can model classes any way you like. Keep in mind what you are building,
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61 don't try to model the real world. This can be confusing, especially because
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62 teachers use real-world objects to explain class relations and you might think
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63 your model should therefore reflect the real world. It doesn't! The model
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64 should match your purpose.
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65
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66 Keep in mind that composition (an object contains other objects) is often
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67 better than inheritance (an object extends another object). Don't waste time
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68 trying to find the optimal class model. Or waste time discussing whether a
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69 square is a rectangle or that a rectangle is a square. It doesn't matter.
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71
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72 ==============================================================================
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73
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74 2. A simple class *Vim9-simple-class*
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75
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76 Let's start with a simple example: a class that stores a text position (see
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77 below for how to do this more efficiently): >
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78
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79 class TextPosition
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80 this.lnum: number
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81 this.col: number
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82
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83 def new(lnum: number, col: number)
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84 this.lnum = lnum
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85 this.col = col
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86 enddef
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87
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88 def SetLnum(lnum: number)
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89 this.lnum = lnum
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90 enddef
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91
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92 def SetCol(col: number)
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93 this.col = col
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94 enddef
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95
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96 def SetPosition(lnum: number, col: number)
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97 this.lnum = lnum
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98 this.col = col
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99 enddef
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100 endclass
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101 < *object* *Object*
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102 You can create an object from this class with the new() method: >
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103
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104 var pos = TextPosition.new(1, 1)
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105
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106 The object members "lnum" and "col" can be accessed directly: >
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107
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108 echo $'The text position is ({pos.lnum}, {pos.col})'
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109 < *E1317* *E1327*
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110 If you have been using other object-oriented languages you will notice that
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111 in Vim the object members are consistently referred to with the "this."
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112 prefix. This is different from languages like Java and TypeScript. The
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113 naming convention makes the object members easy to spot. Also, when a
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114 variable does not have the "this." prefix you know it is not an object member.
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115
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116
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117 Member write access ~
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118
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119 Now try to change an object member directly: >
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120
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121 pos.lnum = 9
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122 < *E1335*
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123 This will give you an error! That is because by default object members can be
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124 read but not set. That's why the TextPosition class provides a method for it: >
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125
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126 pos.SetLnum(9)
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127
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128 Allowing to read but not set an object member is the most common and safest
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129 way. Most often there is no problem using a value, while setting a value may
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130 have side effects that need to be taken care of. In this case, the SetLnum()
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131 method could check if the line number is valid and either give an error or use
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132 the closest valid value.
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133 *:public* *E1331*
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134 If you don't care about side effects and want to allow the object member to be
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135 changed at any time, you can make it public: >
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136
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137 public this.lnum: number
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138 public this.col: number
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139
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140 Now you don't need the SetLnum(), SetCol() and SetPosition() methods, setting
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141 "pos.lnum" directly above will no longer give an error.
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142 *E1334*
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143 If you try to set an object member that doesn't exist you get an error: >
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144 pos.other = 9
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145 < E1334: Object member not found: other ~
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146
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147
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148 Private members ~
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149 *E1332* *E1333*
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150 On the other hand, if you do not want the object members to be read directly,
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151 you can make them private. This is done by prefixing an underscore to the
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152 name: >
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153
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154 this._lnum: number
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155 this._col number
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156
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157 Now you need to provide methods to get the value of the private members.
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158 These are commonly called getters. We recommend using a name that starts with
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159 "Get": >
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160
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161 def GetLnum(): number
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162 return this._lnum
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163 enddef
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164
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165 def GetCol() number
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166 return this._col
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167 enddef
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168
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169 This example isn't very useful, the members might as well have been public.
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170 It does become useful if you check the value. For example, restrict the line
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171 number to the total number of lines: >
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172
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173 def GetLnum(): number
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174 if this._lnum > this._lineCount
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175 return this._lineCount
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176 endif
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177 return this._lnum
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178 enddef
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179
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180
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181 Simplifying the new() method ~
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182
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183 Many constructors take values for the object members. Thus you very often see
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184 this pattern: >
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185
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186 class SomeClass
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187 this.lnum: number
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188 this.col: number
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189
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190 def new(lnum: number, col: number)
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191 this.lnum = lnum
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192 this.col = col
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193 enddef
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194 endclass
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195
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196 Not only is this text you need to write, it also has the type of each member
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197 twice. Since this is so common a shorter way to write new() is provided: >
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198
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199 def new(this.lnum, this.col)
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200 enddef
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201
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202 The semantics are easy to understand: Providing the object member name,
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203 including "this.", as the argument to new() means the value provided in the
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204 new() call is assigned to that object member. This mechanism comes from the
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205 Dart language.
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206
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207 Putting together this way of using new() and making the members public results
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208 in a much shorter class definition as what we started with: >
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209
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210 class TextPosition
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211 public this.lnum: number
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212 public this.col: number
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213
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214 def new(this.lnum, this.col)
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215 enddef
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216
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217 def SetPosition(lnum: number, col: number)
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218 this.lnum = lnum
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219 this.col = col
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220 enddef
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221 endclass
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222
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223 The sequence of constructing a new object is:
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224 1. Memory is allocated and cleared. All values are zero/false/empty.
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225 2. For each declared member that has an initializer, the expression is
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226 evaluated and assigned to the member. This happens in the sequence the
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227 members are declared in the class.
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228 3. Arguments in the new() method in the "this.name" form are assigned.
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229 4. The body of the new() method is executed.
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230
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231 If the class extends a parent class, the same thing happens. In the second
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232 step the members of the parent class are done first. There is no need to call
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233 "super()" or "new()" on the parent.
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234
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235 ==============================================================================
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236
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237 3. class members and functions *Vim9-class-member*
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238
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239 *:static* *E1337* *E1338*
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240 Class members are declared with "static". They are used by the name without a
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241 prefix: >
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242
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243 class OtherThing
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244 this.size: number
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245 static totalSize: number
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246
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247 def new(this.size)
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248 totalSize += this.size
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249 enddef
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250 endclass
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251 < *E1340* *E1341*
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252 Since the name is used as-is, shadowing the name by a function argument name
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253 or local variable name is not allowed.
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254
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255 Just like object members the access can be made private by using an underscore
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256 as the first character in the name, and it can be made public by prefixing
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257 "public": >
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258
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259 class OtherThing
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260 static total: number # anybody can read, only class can write
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261 static _sum: number # only class can read and write
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262 public static result: number # anybody can read and write
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263 endclass
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264 <
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265 *class-function*
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266 Class functions are also declared with "static". They have no access to
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267 object members, they cannot use the "this" keyword. >
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268
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269 class OtherThing
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270 this.size: number
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271 static totalSize: number
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272
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273 # Clear the total size and return the value it had before.
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274 static def ClearTotalSize(): number
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275 var prev = totalSize
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276 totalSize = 0
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277 return prev
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278 enddef
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279 endclass
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280
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281 Inside the class the function can be called by name directly, outside the
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282 class the class name must be prefixed: `OtherThing.ClearTotalSize()`.
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283
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284 ==============================================================================
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285
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286 4. Using an abstract class *Vim9-abstract-class*
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287
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288 An abstract class forms the base for at least one sub-class. In the class
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289 model one often finds that a few classes have the same properties that can be
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290 shared, but a class with these properties does not have enough state to create
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291 an object from. A sub-class must extend the abstract class and add the
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292 missing state and/or methods before it can be used to create objects for.
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293
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294 For example, a Shape class could store a color and thickness. You cannot
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295 create a Shape object, it is missing the information about what kind of shape
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296 it is. The Shape class functions as the base for a Square and a Triangle
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297 class, for which objects can be created. Example: >
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298
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299 abstract class Shape
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300 this.color = Color.Black
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301 this.thickness = 10
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302 endclass
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303
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304 class Square extends Shape
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305 this.size: number
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306
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307 def new(this.size)
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308 enddef
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309 endclass
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310
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311 class Triangle extends Shape
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312 this.base: number
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313 this.height: number
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314
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315 def new(this.base, this.height)
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316 enddef
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317 endclass
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318 <
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319 An abstract class is defined the same way as a normal class, except that it
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320 does not have any new() method. *E1359*
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321
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322
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323 ==============================================================================
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324
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325 5. Using an interface *Vim9-using-interface*
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326
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327 The example above with Shape, Square and Triangle can be made more useful if
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328 we add a method to compute the surface of the object. For that we create the
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329 interface called HasSurface, which specifies one method Surface() that returns
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330 a number. This example extends the one above: >
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331
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332 abstract class Shape
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333 this.color = Color.Black
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334 this.thickness = 10
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335 endclass
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336
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337 interface HasSurface
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338 def Surface(): number
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339 endinterface
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340
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341 class Square extends Shape implements HasSurface
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342 this.size: number
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343
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344 def new(this.size)
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345 enddef
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346
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347 def Surface(): number
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348 return this.size * this.size
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349 enddef
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350 endclass
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351
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352 class Triangle extends Shape implements HasSurface
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353 this.base: number
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354 this.height: number
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355
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356 def new(this.base, this.height)
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357 enddef
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358
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359 def Surface(): number
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360 return this.base * this.height / 2
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361 enddef
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362 endclass
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363
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364 If a class declares to implement an interface, all the items specified in the
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365 interface must appear in the class, with the same types. *E1348* *E1349*
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366
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367 The interface name can be used as a type: >
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368
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369 var shapes: list<HasSurface> = [
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370 Square.new(12),
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371 Triangle.new(8, 15),
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372 ]
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373 for shape in shapes
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374 echo $'the surface is {shape.Surface()}'
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375 endfor
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376
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377
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378 ==============================================================================
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379
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380 6. More class details *Vim9-class* *Class* *class*
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381
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382 Defining a class ~
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383 *:class* *:endclass* *:abstract*
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384 A class is defined between `:class` and `:endclass`. The whole class is
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385 defined in one script file. It is not possible to add to a class later.
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386
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387 A class can only be defined in a |Vim9| script file. *E1316*
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388 A class cannot be defined inside a function.
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389
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390 It is possible to define more than one class in a script file. Although it
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391 usually is better to export only one main class. It can be useful to define
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392 types, enums and helper classes though.
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393
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394 The `:abstract` keyword may be prefixed and `:export` may be used. That gives
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395 these variants: >
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396
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397 class ClassName
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398 endclass
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399
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400 export class ClassName
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401 endclass
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402
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403 abstract class ClassName
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404 endclass
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405
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406 export abstract class ClassName
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407 endclass
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408 <
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409 *E1314*
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410 The class name should be CamelCased. It must start with an uppercase letter.
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411 That avoids clashing with builtin types.
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412 *E1315*
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413 After the class name these optional items can be used. Each can appear only
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414 once. They can appear in any order, although this order is recommended: >
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415 extends ClassName
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416 implements InterfaceName, OtherInterface
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417 specifies SomeInterface
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418 < *E1355*
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419 Each member and function name can be used only once. It is not possible to
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420 define a function with the same name and different type of arguments.
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421
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422
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423 Extending a class ~
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424 *extends*
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425 A class can extend one other class. *E1352* *E1353* *E1354*
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426 The basic idea is to build on top of an existing class, add properties to it.
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427
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428 The extended class is called the "base class" or "super class". The new class
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429 is called the "child class".
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430
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431 Object members from the base class are all taken over by the child class. It
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432 is not possible to override them (unlike some other languages).
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433
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434 *E1356* *E1357* *E1358*
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435 Object methods of the base class can be overruled. The signature (arguments,
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436 argument types and return type) must be exactly the same. The method of the
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437 base class can be called by prefixing "super.".
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438
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439 Other object methods of the base class are taken over by the child class.
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440
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441 Class functions, including functions starting with "new", can be overruled,
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442 like with object methods. The function on the base class can be called by
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443 prefixing the name of the class (for class functions) or "super.".
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444
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445 Unlike other languages, the constructor of the base class does not need to be
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446 invoked. In fact, it cannot be invoked. If some initialization from the base
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447 class also needs to be done in a child class, put it in an object method and
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448 call that method from every constructor().
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449
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450 If the base class did not specify a new() function then one was automatically
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451 created. This function will not be taken over by the child class. The child
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452 class can define its own new() function, or, if there isn't one, a new()
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453 function will be added automatically.
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454
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455
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456 A class implementing an interface ~
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457 *implements* *E1346* *E1347*
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458 A class can implement one or more interfaces. The "implements" keyword can
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459 only appear once *E1350* . Multiple interfaces can be specified, separated by
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460 commas. Each interface name can appear only once. *E1351*
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461
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462
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463 A class defining an interface ~
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464 *specifies*
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465 A class can declare its interface, the object members and methods, with a
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466 named interface. This avoids the need for separately specifying the
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467 interface, which is often done in many languages, especially Java.
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468
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469
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470 Items in a class ~
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471 *E1318* *E1325* *E1326*
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472 Inside a class, in between `:class` and `:endclass`, these items can appear:
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473 - An object member declaration: >
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474 this._memberName: memberType
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475 this.memberName: memberType
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476 public this.memberName: memberType
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477 - A constructor method: >
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478 def new(arguments)
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479 def newName(arguments)
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480 - An object method: >
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481 def SomeMethod(arguments)
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482 < *E1329*
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483 For the object member the type must be specified. The best way is to do this
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484 explicitly with ": {type}". For simple types you can also use an initializer,
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485 such as "= 123", and Vim will see that the type is a number. Avoid doing this
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486 for more complex types and when the type will be incomplete. For example: >
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487 this.nameList = []
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488 This specifies a list, but the item type is unknown. Better use: >
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489 this.nameList: list<string>
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490 The initialization isn't needed, the list is empty by default.
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491 *E1330*
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492 Some types cannot be used, such as "void", "null" and "v:none".
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493
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494
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495 Defining an interface ~
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496 *:interface* *:endinterface*
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497 An interface is defined between `:interface` and `:endinterface`. It may be
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498 prefixed with `:export`: >
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499
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500 interface InterfaceName
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501 endinterface
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502
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503 export interface InterfaceName
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504 endinterface
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505 < *E1344*
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506 An interface can declare object members, just like in a class but without any
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Bram Moolenaar <Bram@vim.org>
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507 initializer.
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508 *E1345*
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509 An interface can declare methods with `:def`, including the arguments and
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Bram Moolenaar <Bram@vim.org>
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510 return type, but without the body and without `:enddef`. Example: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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511
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512 interface HasSurface
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513 this.size: number
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Bram Moolenaar <Bram@vim.org>
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514 def Surface(): number
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515 endinterface
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516
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517 An interface name must start with an uppercase letter. *E1343*
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518 The "Has" prefix can be used to make it easier to guess this is an interface
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519 name, with a hint about what it provides.
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520 An interface can only be defined in a |Vim9| script file. *E1342*
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521
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522
32004
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523 null object ~
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parents: 31885
diff changeset
524
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525 When a variable is declared to have the type of an object, but it is not
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parents: 31885
diff changeset
526 initialized, the value is null. When trying to use this null object Vim often
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parents: 31885
diff changeset
527 does not know what class was supposed to be used. Vim then cannot check if
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parents: 31885
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528 a member name is correct and you will get an "Using a null object" error,
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Bram Moolenaar <Bram@vim.org>
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529 even when the member name is invalid. *E1360* *E1362*
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Bram Moolenaar <Bram@vim.org>
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diff changeset
530
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diff changeset
531
31335
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532 Default constructor ~
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parents:
diff changeset
533
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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534 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
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diff changeset
535 defined. This default constructor will have arguments for all the object
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
536 members, in the order they were specified. Thus if your class looks like: >
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Bram Moolenaar <Bram@vim.org>
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537
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538 class AutoNew
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Bram Moolenaar <Bram@vim.org>
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diff changeset
539 this.name: string
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diff changeset
540 this.age: number
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541 this.gender: Gender
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Bram Moolenaar <Bram@vim.org>
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542 endclass
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parents:
diff changeset
543
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544 Then The default constructor will be: >
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Bram Moolenaar <Bram@vim.org>
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diff changeset
545
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diff changeset
546 def new(this.name = v:none, this.age = v:none, this.gender = v:none)
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547 enddef
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Bram Moolenaar <Bram@vim.org>
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548
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diff changeset
549 The "= v:none" default values make the arguments optional. Thus you can also
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parents: 31430
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550 call `new()` without any arguments. No assignment will happen and the default
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
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551 value for the object members will be used. This is a more useful example,
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
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552 with default values: >
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553
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554 class TextPosition
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parents: 31396
diff changeset
555 this.lnum: number = 1
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diff changeset
556 this.col: number = 1
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557 endclass
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diff changeset
558
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diff changeset
559 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
560 yourself. For example, if for the AutoNew class above you insist on getting
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parents: 31396
diff changeset
561 the name, you can define the constructor like this: >
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Bram Moolenaar <Bram@vim.org>
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562
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Bram Moolenaar <Bram@vim.org>
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563 def new(this.name, this.age = v:none, this.gender = v:none)
31430
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Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
564 enddef
31441
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
565 < *E1328*
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
566 Note that you cannot use another default value than "v:none" here. If you
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
567 want to initialize the object members, do it where they are declared. This
e572ff386670 patch 9.0.1053: default constructor arguments are not optional
Bram Moolenaar <Bram@vim.org>
parents: 31430
diff changeset
568 way you only need to look in one place for the default values.
31430
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Bram Moolenaar <Bram@vim.org>
parents: 31396
diff changeset
569
31671
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Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
570 All object members will be used in the default constructor, also private
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
571 access ones.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
572
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
573 If the class extends another one, the object members of that class will come
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
574 first.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
575
31335
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parents:
diff changeset
576
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
577 Multiple constructors ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
578
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
579 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
580 constructor is often called with the same arguments you may want to simplify
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
581 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
582 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
583
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
584 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
585 enddef
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
586 ...
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
587 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
588 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
589 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
590
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
591 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
592 includes it: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
593
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
594 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
595 this.color = Color.black
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
596 enddef
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
597 ...
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
598 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
599 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
600 var shoes = newBlack(Garment.shoes, "9.5")
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
601
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
602 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
603 "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
604 constructor methods.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
605
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
606
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
607 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
608
31885
cc751d944b7e Update runtime files.
Bram Moolenaar <Bram@vim.org>
parents: 31671
diff changeset
609 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
610
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
611 A type definition is giving a name to a type specification. For Example: >
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
612
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
613 :type ListOfStrings list<string>
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
614
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
615 TODO: more explanation
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
616
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
617
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
618 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
619
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diff changeset
620 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
621
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
622 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
623
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
624 :enum Color
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
625 White
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
626 Red
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
627 Green
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
628 Blue
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
629 Black
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
630 :endenum
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
631
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
632 TODO: more explanation
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
633
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
634
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
635 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
636
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
637 9. Rationale
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
638
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
639 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
640 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
641 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
642 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
643
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
644 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
645 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
646 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
647 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
648 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
649 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
650 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
651
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
652 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
653 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
654 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
655 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
656 understand.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
657
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
658 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
659 - Keep it simple.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
660 - 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
661 - 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
662 - 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
663 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
664 - Keep it consistent.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
665 - Aim at an average size plugin, not at a huge project.
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
666
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
667
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
668 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
669
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
670 Many languages use the class name for the constructor method. A disadvantage
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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parents:
diff changeset
671 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
672 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
673 disadvantage.
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Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
674
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
675 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
676 "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
677 create a new object has no obvious relation with "constructor()".
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
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parents:
diff changeset
678
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
679 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
680 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
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parents:
diff changeset
681 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
682
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
683
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
684 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
685
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
686 In Vim script, both legacy and |Vim9| script, there is no overloading of
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
687 functions. That means it is not possible to use the same function name with
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
688 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
689 constructor.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
690
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
691 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
692 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
693 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
694 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
695 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
696 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
697 returning.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
698
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
699 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
700 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
701 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
702 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
703
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
704
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
705 No overloading of methods ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
706
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
707 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
708 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
709 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
710 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
711 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
712
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
713
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
714 Single inheritance and interfaces ~
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
715
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
716 Some languages support multiple inheritance. Although that can be useful in
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
717 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
718 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
719 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
720 Vim. The "keep it simple" rule applies here.
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
721
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
722 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
723 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
724 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
725 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
726 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
727 brittle and leads to obscure problems, let's not do that.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
728
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
729
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
730 Using "this.member" everywhere ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
731
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
732 The object members in various programming languages can often be accessed in
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
733 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
734 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
735 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
736
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
737 A very common issue is that in the constructor the arguments use the same name
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
738 as the object member. Then for these members "this." needs to be prefixed in
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
739 the body, while for other members this is not needed and often omitted. This
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
740 leads to a mix of members with and without "this.", which is inconsistent.
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 For |Vim9| classes the "this." prefix is always used. Also for declaring the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
743 members. Simple and consistent. When looking at the code inside a class it's
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
744 also directly clear which variable references are object members and which
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
745 aren't.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
746
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
747
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
748 Using class members ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
749
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
750 Using "static member" to declare a class member is very common, nothing new
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
751 here. In |Vim9| script these can be accessed directly by their name. Very
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
752 much like how a script-local variable can be used in a function. Since object
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
753 members are always accessed with "this." prepended, it's also quickly clear
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
754 what kind of member it is.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
755
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
756 TypeScript prepends the class name before the class member, also inside the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
757 class. This has two problems: The class name can be rather long, taking up
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
758 quite a bit of space, and when the class is renamed all these places need to
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
759 be changed too.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
760
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
761
31671
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
762 Declaring object and class members ~
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
763
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
764 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
765 TypeScript does not use it: >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
766 class Point {
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
767 x: number;
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
768 y = 0;
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
769 }
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
770
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
771 Following that Vim object members could be declared like this: >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
772 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
773 this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
774 this.y = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
775 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
776
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
777 Some users pointed out that this looks more like an assignment than a
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
778 declaration. Adding "var" changes that: >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
779 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
780 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
781 var this.y = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
782 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
783
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
784 We also need to be able to declare class members using the "static" keyword.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
785 There we can also choose to leave out "var": >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
786 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
787 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
788 static count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
789 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
790
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
791 Or do use it, before "static": >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
792 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
793 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
794 var static count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
795 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
796
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
797 Or after "static": >
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
798 class Point
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
799 var this.x: number
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
800 static var count = 0
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
801 endclass
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
802
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
803 This is more in line with "static def Func()".
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
804
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
805 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
806 reasons to leave it out are:
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
807 1. TypeScript, Java and other popular languages do not use it.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
808 2. Less clutter.
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
809
5ed19049b1e8 Update runtime files
Bram Moolenaar <Bram@vim.org>
parents: 31579
diff changeset
810
31335
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
811 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
812
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
813 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
814 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
815 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
816 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
817
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
818 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
819 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
820 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
821 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
822
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
823
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
824 Default read access to object members ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
825
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
826 Some users will remark that the access rules for object members are
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
827 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
828 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
829 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
830 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
831 objects.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
832
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
833 When adding object members one usually doesn't think much about this, just get
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
834 the type right. And normally the values are set in the new() method.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
835 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
836 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
837 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
838
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
839
31396
307f68a41b03 patch 9.0.1031: Vim9 class is not implemented yet
Bram Moolenaar <Bram@vim.org>
parents: 31335
diff changeset
840 Making object members 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
841
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
842 When an object member is private, it can only be read and changed inside the
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
843 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
844 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
845 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
846
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
847 In case you change your mind and want to make the object member accessible
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
848 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
849 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
850 to find and change.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
851
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
852 The other way around is much harder: you can easily prepend an underscore to
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
853 the object member inside the class to make it private, but any usage elsewhere
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
854 you will have to track down and change. You may have to make it a "set"
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
855 method call. This reflects the real world problem that taking away access
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
856 requires work to be done for all places where that access exists.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
857
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
858 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
859 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
860 number of keywords.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
861
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
862
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
863 No protected object members ~
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
864
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
865 Some languages provide several ways to control access to object members. The
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
866 most known is "protected", and the meaning varies from language to language.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
867 Others are "shared", "private" and even "friend".
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
868
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
869 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
870 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
871 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
872
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
873 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
874 small team working on it. Complex rules then only make it more complicated,
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
875 the extra safety provide by the rules isn't really needed. Let's just keep it
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
876 simple and not specify access details.
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
877
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 ==============================================================================
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
880
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
881 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
882
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
883 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
884 the restrictions?
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
885
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
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diff changeset
886 Thoughts:
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
887 - 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
888 - 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
889 - 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
890
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
891 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
892 - For testing: Mock mechanism
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
893
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
894 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
895 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
896 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
897 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
898
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
899
5acc0d2cf4f7 patch 9.0.1001: classes are not documented or implemented yet
Bram Moolenaar <Bram@vim.org>
parents:
diff changeset
900 vim:tw=78:ts=8:noet:ft=help:norl: