在VBA中克隆对象？ [英] Cloning Objects in VBA?

问题描述

是否存在在VBA中克隆对象的通用方法？这样我可以将x复制到y而不是仅复制指针？

Is there a generic way to clone objects in VBA? So that i could copy x to y instead of copying just the pointer?

  Dim x As New Class1
  Dim y As Class1

  x.Color = 1
  x.Height = 1

  Set y = x
  y.Color = 2

  Debug.Print "x.Color=" & x.Color & ", x.Height=" & x.Height

通过泛型，我的意思是类似 Set y = CloneObject（x ），而不是必须为类创建自己的方法来逐一复制其属性。

By generic i mean something like Set y = CloneObject(x) rather than having to create my own method for the class copying its properties one by one.

推荐答案

确定，这是说明它的开始：

OK, here's the beginning of something that illustrates it:

创建一个类，将其命名为 Class1：

Create a class, call it, oh, "Class1":

Option Explicit

Public prop1 As Long
Private DontCloneThis As Variant

Public Property Get PrivateThing()
    PrivateThing = DontCloneThis
End Property

Public Property Let PrivateThing(value)
    DontCloneThis = value
End Property

现在我们需要给它一个Clone函数。在另一个模块中，尝试以下操作：

Now we need to give it a Clone function. In another module, try this:

Option Explicit

Option Explicit

Public Sub makeCloneable()

Dim idx As Long
Dim line As String
Dim words As Variant
Dim cloneproc As String

' start building the text of our new function
    cloneproc = "Public Function Clone() As Class1" & vbCrLf
    cloneproc = cloneproc & "Set Clone = New Class1" & vbCrLf

    ' get the code for the class and start examining it    
    With ThisWorkbook.VBProject.VBComponents("Class1").CodeModule

        For idx = 1 To .CountOfLines

            line = Trim(.lines(idx, 1)) ' get the next line
            If Len(line) > 0 Then
                line = Replace(line, "(", " ") ' to make words clearly delimited by spaces
                words = Split(line, " ") ' so we get split on a space
                If words(0) = "Public" Then ' can't set things declared Private
                    ' several combinations of words possible
                    If words(1) = "Property" And words(2) = "Get" Then
                        cloneproc = cloneproc & "Clone." & words(3) & "=" & words(3) & vbCrLf
                    ElseIf words(1) = "Property" And words(2) = "Set" Then
                        cloneproc = cloneproc & "Set Clone." & words(3) & "=" & words(3) & vbCrLf
                    ElseIf words(1) <> "Sub" And words(1) <> "Function" And words(1) <> "Property" Then
                        cloneproc = cloneproc & "Clone." & words(1) & "=" & words(1) & vbCrLf
                    End If
                End If
            End If
        Next

        cloneproc = cloneproc & "End Function"

        ' put the code into the class
        .AddFromString cloneproc

    End With

End Sub

运行该命令，并将以下内容添加到Class1中

Run that, and the following gets added into Class1

Public Function Clone() As Class1
Set Clone = New Class1
Clone.prop1 = prop1
Clone.PrivateThing = PrivateThing
End Function

...看起来像一个开始。我会整理很多东西（可能会整理-事实证明这很有趣）。一个很好的正则表达式，用于查找gettable / lettable / settable属性，将其重构为几个小函数，删除旧的 Clone函数的代码（并将新函数放在最后），对DRY来说有点Stringbuilder式的（唐） t重复自己的操作），诸如此类。

...which looks like a start. Lots of things I'd clean up (and probably will - this turned out to be fun). A nice Regular Expression to find gettable/lettable/settable attributes, refactoring into several small functions, code to remove old "Clone" functions (and put the new one at the end), something a bit more Stringbuilder-ish to DRY (Don't Repeat Yourself) up the concatenations, stuff like that.

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