Passing objects ByRef or ByVal

[confusion123]

In this article,

Passing Objects: ByRef / ByVal

it is claimed objects can ONLY be passed ByRef, (the second comment in the article) but the third comment states the following:

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range) 

     'code

End Sub

so which is correct? Objects are passed ByRef or ByVal?

Thanks

 

[Andrew Poulsom]

There's a good explanation here:

Passing Variable ByRef And ByVal

 

[Kyle123]

That's not strictly true in practice. When one is referring to an object, the byVal/byRef refers to the pointer of the object. To all intents and purposes this in effect means that objects are only passed byRef, there are situations however that this can catch you out. Consider:

Sub test()
    
    Dim b As Collection
    Set b = New Collection
    
    If b Is Nothing Then
        Debug.Print "Object is Nothing"
    End If
    
    DeleteObjectVal b
    
    If b Is Nothing Then
        Debug.Print "Object is Nothing"
    End If
    
    DeleteObjectRef b
    
    If b Is Nothing Then
        Debug.Print "Object is Nothing"
    End If
    
End Sub

Sub DeleteObjectVal(ByVal obj As Object)
    Set obj = Nothing
End Sub

Sub DeleteObjectRef(ByRef obj As Object)
    Set obj = Nothing
End Sub

 

[RoryA]

Objects are always passed as a pointer to a memory location. If you pass an object ByVal, you pass a copy of the pointer, not a copy of the object. That means that you can still access all properties/methods of the object but you cannot change the original pointer to refer to a different object.

 

[confusion123]

Thanks for all the feedback.