VBA - CallByName won't accept variant arguments

Question

Solution: Just put brackets around Value in the CallByName statement to force evaluation of it.

Ex. CallByName MobClass, TargetData, vbLet, (Valu

Answer 1

The Problem is that you pass the properties-arguments by reference not by value, but you can't pass a reference to a different datatype (variant -> long) as the types don't match and it can't be converted as this would change the data type in the caller too. By using brackets, you force the argument to be passed by value and it can be casted as typeLong.

You can avoid this by using ByValin theProperty Letterinstead ofByRef(what is implicit used if not set). You are aware that by referencing a variable, changes made in the property change the callers value too?

Example:

Class PassExample

'Save as class module PassExample
Public Property Let PropByVal(ByVal NewVal As Long)
NewVal = 1
End Property
Public Property Let PropByRef(ByRef NewVal As Long)
NewVal = 1
End Property 

Module with test sub:

'save as standard module
Sub test()
Dim v As Variant
v = 0

Dim ExampleInstance As New PassExample

CallByName ExampleInstance, "PropByVal", VbLet, v 'this works
CallByName ExampleInstance, "PropByRef", VbLet, v 'type mismatch
CallByName ExampleInstance, "PropByRef", VbLet, (v) 'this works as ByRef is changed to byval
Debug.Print v ' shows 0, not 1 as it should be if referenced

CallByName ExampleInstance, "PropByRef", VbLet, CVar(v) ' works too as it passes a function-result that can't be referenced

End Sub

Thanks to Rory and chris neilsen for providing the solution!