VB Forum / General 2 / November 2004

Never heard about it...

Can it be that you mean "Inheritance by Containment"?

Meaning that you include an instance og an existing class
in your new one, thereby getting access to (inheriting) all
its methods & attributes?

something like this:

' --- Parent (Contained) class -------------------------
private m_sName As String

Public Property let Name(byval s As String)
   m_sName = s
End property

Public Property Get Name() As String
   Name = m_sName
End property

Public Sub Print()
   Debug.Print Me.Name
End Sub

' --- Child (containing) class -------------------------
private m_sPhone As String
private m_oParent as CParent

Public Property let Phone(byval s As String)
   m_sPhone = s
End property

Public Property Get Phone() As String
   Phone = m_sPhone
End property

' Here I make wrapper methods for Parent, to
' Completely hide the containment.
Public Property let Name(byval s As String)
   m_oParent.Name = s
End property

Public Property Get Name() As String
   Name = m_oParent.Name
End property

Public Sub Print()
   Debug.Print m_oParent.Name
   Debug.print Me.Phone
End Sub

' Another alternative, is to expose the contained class like this:
Public Property Get Parent() as CParent
   Set Parent = m_oParent
End Property

Private Sub Class_Initialize()
   Set m_oParent = New CParent
End Sub

Private Sub Class_Terminate()
   Set m_oParent = Nothing
End Sub

' ----------Use ------------
...
Dim m_oChild as CChild
Set m_oChild = New CChild

m_oChild.Name = "Dag"
m_oChild.Phone = "370 12 666"
m_oChild.Print

' Or with an exposed parent:
m_oChild.Parent.Name = "Dag"
m_oChild.Phone = "370 12 666"
m_oChild.Print
...