Base Class Method to use Shadow'ed member variable of Derived Class?

[Joe HM]

Hello -

I have a function in a base class that I want to use the shadow'ed
member variable of the derived class. Here is the code ...

Public Class cCaptureBase
Protected Const cDummy As String = "Base"

Overridable Sub print()
Console.WriteLine(cDummy)
End Sub
End Class

Public Class cCaptureDerived
Inherits cCaptureBase

Protected Shadows Const cDummy As String = "Derived"
End Class

Sub Main()

Dim lInstance As cCaptureBase
lInstance = New cCaptureDerived

lInstance.print()

I would like print() to print the cDummy of the cCaptureDerived class.
Is there any way of doing that? I know I could override the print() in
the derived class but I would like to keep that in the base class.

This might either be something very simple or something that should not
be done in proper OO design. Any suggestions?

Thanks!
Joe

 

[Larry Lard]

Hello -

I have a function in a base class that I want to use the shadow'ed
member variable of the derived class. Here is the code ...

Public Class cCaptureBase
Protected Const cDummy As String = "Base"

Overridable Sub print()
Console.WriteLine(cDummy)
End Sub
End Class

Public Class cCaptureDerived
Inherits cCaptureBase

Protected Shadows Const cDummy As String = "Derived"
End Class

Sub Main()

Dim lInstance As cCaptureBase
lInstance = New cCaptureDerived

lInstance.print()

I would like print() to print the cDummy of the cCaptureDerived class.
Is there any way of doing that? I know I could override the print() in
the derived class but I would like to keep that in the base class.

This might either be something very simple or something that should not
be done in proper OO design. Any suggestions?

A good rule of thumb is that a design that requires the use of
'Shadows' is doing something wrong.

Try this:

Public Class BaseClass
Protected Overridable ReadOnly Property Dummy() As String
Get
Return "base"
End Get
End Property

Public Overridable Sub Print()
Console.WriteLine(Me.Dummy)
End Sub

End Class

Public Class DerivedClass
Inherits BaseClass

Protected Overrides ReadOnly Property Dummy() As String
Get
Return "derived"
End Get
End Property

End Class

Module Module1

Sub Main()

Dim instance As BaseClass = New DerivedClass

instance.Print()

Console.ReadLine()
End Sub

End Module

 

[Joe HM]

D'oh ... right ... I forgot about the Property!

Thanks for the help ... and I will avoid "Shadows" in the future ...

Joe