Delphi 的接口(2) - 第一个例子

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.
}