unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
  end;

  IMyInterface1 = interface
    function Func1: Integer;
    function Func2: Integer;
  end;

  IMyInterface2 = interface
    procedure Proc1;
    procedure Proc2;
  end;

  TMyClass1 = class(TInterfacedObject, IMyInterface1, IMyInterface2)
  public
    procedure Proc1;
    procedure Proc2;
    function Func1: Integer;
    function Func2: Integer;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TMyClass1 }

function TMyClass1.Func1: Integer;
begin
  ShowMessage('IMyInterface1.Func1');
  Result := 0;
end;

function TMyClass1.Func2: Integer;
begin
  ShowMessage('IMyInterface1.Func2');
  Result := 0;
end;

procedure TMyClass1.Proc1;
begin
  ShowMessage('IMyInterface2.Proc1');
end;

procedure TMyClass1.Proc2;
begin
  ShowMessage('IMyInterface2.Proc2');
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  c: TMyClass1;
begin
  c := TMyClass1.Create;

  c.Func1;
  c.Func2;

  c.Proc1;
  c.Proc2;

  c.Free;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  i1: IMyInterface1;
begin
  i1 := TMyClass1.Create;
  i1.Func1;
  i1.Func2;
end;

procedure TForm1.Button3Click(Sender: TObject);
var
  i2: IMyInterface2;
begin
  i2 := TMyClass1.Create;
  i2.Proc1;
  i2.Proc2;
end;

procedure TForm1.Button4Click(Sender: TObject);
var
  c: TMyClass1;
  i1: IMyInterface1;
  i2: IMyInterface2;
begin
  c := TMyClass1.Create;

  i1 := c;
  i1.Func1;
  i1.Func2;

  i2 := c;
  i2.Proc1;
  i2.Proc2;

//  c.Free; {}
end;

end.

{
  1、接口命名约定 I 起头, 就像类从 T 打头一样.

  2、接口都是从 IInterface 继承而来; 若是从根接口继承, 可省略.

  3、接口成员只能是方法、属性, 没有字段.

  4、接口成员都是公开的, 不需要 private、protected、public、published 等任何访问限制.

  5、因为接口只声明、无实现, 也用不到继承与覆盖相关的修饰(virtual、dynamic、abstract、override).

  6、一个接口可以从另一个接口继承, 但不能从多个接口继承; 不过 Delphi.Net 已支持接口的多继承了.

  7、一个类可以实现多个接口: TMyClass = class(父类, 接口1, 接口2, ...)  end;

  8、不过实现接口的类有多么丰富, 接口只拥有自己声明的成员.

  9、实现接口的类一般继承于 TInterfacedObject, 直接从 TObject 继承会增加一些麻烦而重复的工作.

  10、接口在用完后会自释放, 并同时释放拥有它的类; 这很方便, 但同时带来很多问题.
}