VBA - Is it possible to pass an Object's property as an argument in a method? - vba

Question

I'm pretty used to VBA, not that much for Objects though and I'm hitting a wall right now...
My config class has almost 100 properties, so I'll not spam them here as the details doesn't really matter for my question.
I hoped to code a duplicate function, to create multiple objects from one and then assign different values for a specific property of each new objects (add new elements to the configurations, so it generates new configs), that would look like this :
Public Function Duplicate(SrcCfg As Config, PropertyName As String, Properties As String) As Collection
Dim Cc As Collection, _
Cfg As Config, _
TotalNumber As Integer, _
A() As String
Set Cc = New Collection
A = Split(Properties, "/")
TotalNumber = UBound(A)
For i = 0 To TotalNumber
'Create a copy of the source object
Set Cfg = SrcCfg.Copy
'Set the property for that particular copy
Cfg.PropertyName = A(i)
'Add that copy to the collection
Cc.Add ByVal Cfg
Next i
Duplicate = Cc
End Function
But I'm not sure that a collection is the best output (as I'll take the results and incorporate them into another master collection), so I'm open to suggestions.
And I'm pretty sure that we can't pass a Property as an argument (I spent quite some times looking for a solution for this...) and I don't know what to do about it as this would be super practical for me. So if there is a solution or a workaround, I'll gladly try it!
Here is the rest of my methods :
Friend Sub SetConfig(SrcConfig As Config)
Config = SrcConfig
End Sub
Public Function Copy() As Config
Dim Result As Config
Set Result = New Config
Call Result.SetConfig(Config)
Set Copy = Result
End Function
Final code to duplicate object :
Working smoothly :
Private Cfg As Config
Friend Sub SetConfig(SrcConfig As Config)
Set Cfg = SrcConfig
End Sub
Public Function Copy() As Config
Dim Result As Config
Set Result = New Config
Call Result.SetConfig(Cfg)
Set Copy = Result
End Function
Public Function Duplicate(PropertyName As String, Properties As String) As Collection
Dim Cc As Collection, _
Cfg As Config, _
TotalNumber As Integer, _
A() As String
Set Cc = New Collection
A = Split(Properties, "/")
TotalNumber = UBound(A)
For i = 0 To TotalNumber
'Create a copy of the source object
Set Cfg = Me.Copy
'Set the property for that particular copy
CallByName Cfg, PropertyName, VbLet, A(i)
'Add that copy to the collection
Cc.Add Cfg
Next i
Set Duplicate = Cc
End Function

Answer 1

You actually got it right, including the types (String).
Just replace your
Cfg.PropertyName = A(i)
with
CallByName Cfg, PropertyName, vbLet, A(i)
The property name must be passed as a string, not a reference or a lambda or anything, so no type safety or compiler aid here. You will have a runtime error if you misspell the name.
As for the return type, VBA does not have lists, so a collection is generally fine, but because in your particular case you know in advance how many objects you will be returning, you can declare an array:
Dim Cc() As Config
ReDim Cc(1 to TotalNumber)
You could declare an array in any case, but if you didn't know the total number, you'd be reallocating it on every iteration.