unit Unit1;

interface

uses

 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls;

type

   //定义接口如果接口独立成一个文件，则在应用程序中和实现程序中都要引用该接口文件；

    ICar = interface (IInterface)

        ['{ED52E264-6683-11D7-B847-001060806215}']

        procedure drive;

    end;

 

//接口实现类1，一定要加入TinterfacedObject才能使用；

    TCar = class(TInterfacedObject,ICar)

    public

        procedure drive;

    end;

//接口实现类2，一定要加入TinterfacedObject才能使用；

    THouseCar = class(TInterfacedObject,ICar)

    public

        procedure drive;

    end;

 

 TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

 private

    { Private declarations }

 public

    { Public declarations }

    function getCar:ICar; //此处可用别的方式来实现获取ICAR，如放在DLL文件中；

 end;

 

var

 Form1: TForm1;

 

implementation

 

{$R *.dfm}

 

{ TCar }

procedure TCar.drive;

begin

 ShowMessage('TCar.drive');

end;

 

{ THouseCar }

procedure THouseCar.drive;

begin

   ShowMessage('THouseCar.drive');

end;

 

procedure TForm1.Button1Click(Sender: TObject);

var

 s:ICar;

begin

 s:= getCar;

 s.drive;

end;

 

function TForm1.getCar:ICar;

begin

   Result:=THouseCar.Create; //此处为整个实现的关键点；

//或Result:=TCar.Create;

end;

 

end.