Implementing an interface via a helper

FormHelperInterface.pas

unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.Controls.Presentation, FMX.StdCtrls;

type
  ITest = interface(IInterface)
    ['{685D7A67-35B5-4D53-B568-3F3AD21A6A53}']
    procedure Test;
  end;

  TFormHelper = class helper for TForm
  public
    procedure Test;
  end;

  TForm1 = class(TForm, ITest)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}


{ TFormHelper }

procedure TFormHelper.Test;
begin
  Sleep(0); // Put breakpoint here
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  (Self as ITest).Test;
end;

end.