Counting references

Let’s take another look at the B-- implementation of CHardway. Our first look concentrated on QueryInterface. This time we’ll focus on AddRef and Release:

‘ CHardway (CLSID_CHardway)
Implements IID_IHardway   ‘ Every class implements default interface 
Implements IID_IUnknown   ‘ Every interface implements IUnknown
                          ‘ Any class can implement additional interfaces
§ 

’ Private variables
Private c As Long         ‘ Internal reference count 

Function IUnknown_QueryInterface(iid As GUID) As Object
§

Sub IUnknown_AddRef()
    c = c + 1
End Sub

Sub IUnknown_Release()
    c = c - 1
    If c = 0 Then 
        RaiseEvent Me.Class_Terminate
        Erase Me
    End If
End Sub

’ The rest of the class
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This code is speculative because there isn’t really a B-- to write it with. In particular, the Erase Me statement in Release is based on the speculation that the object was originally allocated with ReDim.