unit Unit1;

interface

uses

  Windows,

  Messages,

  SysUtils,

  Variants,

  Classes,

  Graphics,

  Controls,

  Forms,

  Dialogs,

  StdCtrls;

type

  // 父接口

  IGreetable = interface

    ['{FE5A34E5-21AB-4120-971B-FDC3241AD55D}']

    // 用于返回一段文本

    function SayHello: string;

  end;

  TMan = class(TObject, IGreetable)

    function SayHello: string;

    // 接口都会有的3个函数(QueryInterface，_AddRef，_Release)

    function QueryInterface(const IID: TGUID; out Obj): HResult; stdcall;

    function _AddRef: Integer; stdcall;

    function _Release: Integer; stdcall;

  end;

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  private

    // 弹出一段文本

    procedure Greeting(Intf: IGreetable);

    {Private declarations}

  public

    {Public declarations}

  end;

var

  Form1: TForm1;

implementation

{$R *.DFM}

// 这里实现自己定义的_AddRef、_Release和QueryInterface方法

// 用于查找接口

function TMan.QueryInterface(const IID: TGUID; out Obj): HResult;

begin

  // 找到返回0，找不到返回'No such interface supported'

  if GetInterface(IID, Obj) then

    Result :=

  else

    Result := Windows.E_NoInterface;

end;

// 接口调用计数

function TMan._AddRef: Integer;

begin

  Result := -

end;

// 接口释放计数

function TMan._Release: Integer;

begin

  Result := -

end;

// 客户函数，返回一段文本

function TMan.SayHello: string;

begin

  Result := 'Hello';

end;

procedure TForm1.Greeting(Intf: IGreetable);

begin

  // 输出一段话

  ShowMessage(Intf.SayHello);

end;

procedure TForm1.Button1Click(Sender: TObject);

var

  // 定义一个父接口

  Intf: IGreetable;

begin

  // 子接口创建

  Intf := TMan.Create;

  // 调用的是子接口中的Greeting函数

  Greeting(Intf);

end;

end.