PRB: Error 459 Trying to Use Alternate Object Interface

MORE INFORMATION

Steps to Reproduce Behavior

1. Create a form with a command button and two class modules (Base_Class and Derived_Class).
2. Add the following code to the Base_Class class module:

         Event Alert(ByVal Msg As String)
   
         Public Sub PostAlert(ByVal Msg As String)
         End Sub
   
   						

3. Add the following code to the Derived_Class class module:

         Implements Base_Class
   
         Event Alert(ByVal Msg As String)
   
         Private Sub Base_Class_PostAlert(ByVal Msg As String)
           RaiseEvent Alert(Msg)
         End Sub
   
   						

4. In the form module, add the following code:

         Dim WithEvents objDC As Derived_Class, WithEvents objBC As Base_Class
   
         Sub Command1_Click()
           Set objDC = New Derived_Class
           Set objBC = objDC              ' error 459 occurs on this line
           objBC.PostAlert "Some Message"
           Set objBC = Nothing
           Set objDC = Nothing
         End Sub
   
         Sub DC_Alert(ByVal Msg As String)
           MsgBox Msg
         End Sub
   
   						

• If you remove the WithEvents keyword from the objBC variable declaration, the code will run.
• If you remove the Event declaration in the Base_Class class module, the compiler will also require you to remove the WithEvents keyword on the variable declaration, and the code will run.
• If you remove the Event declaration in the Derived_Class class module, you will get a compile error.
• You cannot implement the Derived_Class event handler as a Private event or derived event as you can with methods. For example, either of the following in the Derived_Class class module will result in a compile error:

        Private Event Base_Class_Alert(ByVal Msg As String)
        Event Base_Class_Alert(ByVal Msg As String)