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Hi, I'm experimenting some interface design and came up with the following: I would like to query a BaseClass instance if it supports a given interface, without freeing the class! As the example below, my great grand child class can support an interface, but I don't want to include the class definition ( great grand child class ) in the Base class.. So, by defining interfaces, I can write exactly what I want: TMyFrame = Class( TBaseFrame, {SupportedInterfaces}) In the code below procedure TForm22.Button1Click(Sender: TObject); begin if Supports( fBaseFrameClass, ISupportTask ) then (fBaseFrame as ISupportTask).CheckTask; end; No matter what overload Support method I call, fBaseFrame is freed once the method exits. Is there a way to know if my class instance supports an interface and call the corresponding method without messing ref counting and free the class instance prematurely? unit frm.main; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls; type ISupportTask = Interface ['{3F785F20-7C44-4163-B55C-5EA267C7204E}'] function CheckTask : Boolean; end; ISupportList = Interface ['{9B7D95E1-DA96-475A-9A1C-910CAF99E5F5}'] function ListCount : Integer; End; ISupportItem = Interface ['{ACADFA2F-3500-4ACB-8049-F49FAC38EFB2}'] function SaveItem : Boolean; End; TBaseFrame = Class( TInterfacedObject ) protected fDummy : Boolean; End; TBaseFrameClass = Class of TBaseFrame; TMyFrame = Class( TBaseFrame, ISupportTask, ISupportList, ISupportItem ) public function CheckTask : Boolean; function ListCount : Integer; function SaveItem : Boolean; destructor Destroy; override; End; TForm22 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); private { Private declarations } fBaseFrameClass : TBaseFrameClass; fBaseFrame : TBaseFrame; public { Public declarations } end; var Form22: TForm22; implementation {$R *.dfm} procedure TForm22.Button1Click(Sender: TObject); begin if Supports( fBaseFrameClass, ISupportTask ) then (fBaseFrame as ISupportTask).CheckTask; end; { TMyFrame } function TMyFrame.CheckTask: Boolean; begin Result := True; end; destructor TMyFrame.Destroy; begin fDummy := True; inherited; end; function TMyFrame.ListCount: Integer; begin Result := 42; end; function TMyFrame.SaveItem: Boolean; begin Result := False; end; procedure TForm22.FormCreate(Sender: TObject); begin fBaseFrameClass := TMyFrame; fBaseFrame := fBaseFrameClass.Create; end; procedure TForm22.FormDestroy(Sender: TObject); begin fBaseFrame.Free; end; end.