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
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.
OK, here's the beginning of something that illustrates it:
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
Now we need to give it a Clone function. In another module, try this:
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
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
...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.
Scott Whitlock has posted a fantastic answer to this problem on another question.
I don't think there's anything built in, although it would be nice.
I think there should at least be a way to create a Clone method automatically using the VBA Editor. I'll see if I can take a look at it once I've got the kids to bed...
