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.