1: { TDerive }

   2:  

   3: constructor TDerive.Create;

   4: begin

   5:   FTest:= 55;

end;

   7:  

   8: procedure TDerive.TalkBase;

   9: begin

'Derive say base');

end;

  12:  

  13: procedure TDerive.TalkDerive;

  14: begin

'Derive');

end;

  17:  

  18: { TBase }

  19:  

  20: procedure TBase.TalkBase;

  21: begin

'Base');

end;

Add(Obj: IBase);

begin

Add(Pointer(Obj))

end;

procedure TForm2.btnTestClick(Sender: TObject);

begin

//加两个

Create;

Add(A);

Create;

Add(A);

//使用

   9:   A:= TDerive(FList[0]);

//我们预期是55

end;

//使用

   2:   A:= TDerive(IBase(FList[0]));

   3:   ShowMessage(IntToStr(A.FTest));//我们预期是55