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Hi mates, I have something on my mind but I couldn't implement it correctly, imagine a generic interface, some classes inherited from that interface, and one method in each class with the same name, now I'm trying to use this interface type every where for different approaches but it doesn't compile correctly. Please have a look at the code if you get a chance and share your thoughts with me, I do appreciate you in advance. The question is how can I implement such an idea properly and safely? I have attached a sample project to save you time too. unit Unit1; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, System.Rtti; type IMyInterface<T> = interface function DoSomething: T; end; TMyClass<T> = class(TInterfacedObject, IMyInterface<T>) function DoSomething: T; end; TForm1 = class(TForm) procedure FormCreate(Sender: TObject); private { Private declarations } function UseInterface<T>(obj: IMyInterface<T>): T; public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} { TMyClass<T> } function TMyClass<T>.DoSomething: T; var ctx: TRttiContext; typ: TRttiType; begin ctx := TRttiContext.Create; typ := ctx.GetType(TypeInfo(T)); if typ.TypeKind = tkInteger then Result := 20 // E2010 Incompatible types: 'T' and 'Integer' else if typ.TypeKind = tkString then Result := T('Hello') // E2089 Invalid typecast else if typ.AsInstance.MetaclassType.InheritsFrom(TStringList) then Result := (typ.AsInstance.MetaclassType.InitInstance(typ) as TStringList) //E2010 Incompatible types: 'T' and 'TStringList' else Result := Default(T); ctx.Free; end; { TForm1 } function TForm1.UseInterface<T>(obj: IMyInterface<T>): T; begin Result := obj.DoSomething; end; procedure TForm1.FormCreate(Sender: TObject); var obj1: IMyInterface<Integer>; obj2: IMyInterface<String>; obj3: IMyInterface<TStringList>; begin try obj1 := TMyClass<Integer>.Create; obj2 := TMyClass<String>.Create; obj3 := TMyClass<TStringList>.Create; ShowMessage(UseInterface<Integer>(obj1).ToString); ShowMessage(UseInterface<String>(obj2)); ShowMessage(UseInterface<TStringList>(obj3).Text); except on E: Exception do Writeln('Exception: ', E.ClassName, ': ', E.Message); end; end; end. Generic Interface.zip