Author: Peter Below

If I want automatic garbage collection with interfaces, I use TInterfacedObject as 
base class. What should I use, if I don't want automatic destruction? Is there a 
similar common base class or do I have to implement the IInterface methods myself?

Answer:

{BaseNonRefcountIntfObjU:
This unit provides a base class with a non-reference counted
implementation of IUnknown.

Author: Dr. Peter Below
Version 1.0, created 28 März 2002
Last modified: 28 März 2002}

1   unit BaseNonRefcountIntfObjU;
2   
3   interface
4   
5   type
6     {Derive classes that need a non-reference counted IUNknown
7     implementation from this class.}
8     TNonRefcountInterfacedObject = class(TObject, IUnknown)
9     protected
10      {IUnknown}
11      function QueryInterface(const IID: TGUID; out Obj): HResult; stdcall;
12      function _AddRef: Integer; stdcall;
13      function _Release: Integer; stdcall;
14    end;
15  
16  implementation
17  
18  uses
19    Windows;
20  
21  function TNonRefcountInterfacedObject.QueryInterface(const IID: TGUID; out Obj):
22    HResult;
23  begin
24    if GetInterface(IID, Obj) then
25      Result := S_OK
26    else
27      Result := E_NOINTERFACE;
28  end;
29  
30  function TNonRefcountInterfacedObject._AddRef: Integer;
31  begin
32    Result := -1; {-1 indicates no reference counting is taking place}
33  end;
34  
35  function TNonRefcountInterfacedObject._Release: Integer;
36  begin
37    Result := -1; {-1 indicates no reference counting is taking place}
38  end;
39  
40  end.