Delphi的接口（5） - 一样的接口、不一样的实现

Delphi的接口（5） - 一样的接口、不一样的实现2012-12-12 博客园万一代码文件:

unit Unit1;

interface

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

type
 TForm1 = class（TForm）
  Button1: TButton;
  procedure Button1Click（Sender: TObject）;
 end;

 IMyInterface1 = interface
  function Func（a,b: Integer）: Integer;
 end;

 TAdd = class（TInterfacedObject, IMyInterface1）
 public
  function Func（a: Integer; b: Integer）: Integer;
  destructor Destroy; override;
 end;

 TMul = class（TInterfacedObject, IMyInterface1）
 public
  function Func（a: Integer; b: Integer）: Integer;
  destructor Destroy; override;
 end;

var
 Form1: TForm1;

implementation

{$R *.dfm}

{ TAdd }

destructor TAdd.Destroy;
begin
 ShowMessage（"TAdd.Destroy"）;
 inherited;
end;

function TAdd.Func（a, b: Integer）: Integer;
begin
 Result := a + b;
end;

{ TMul }

destructor TMul.Destroy;
begin
 ShowMessage（"TMul.Destroy"）;
 inherited;
end;

function TMul.Func（a, b: Integer）: Integer;
begin
 Result := a * b;
end;

{ TForm1 }

procedure TForm1.Button1Click（Sender: TObject）;
var
 I: IMyInterface1;
begin
 I := TAdd.Create;
 ShowMessage（IntToStr（I.Func（9, 9）））; {18}

 I := TMul.Create; {I 在指向新的目标前会先释放前面所属的类}
 ShowMessage（IntToStr（I.Func（9, 9）））; {81}
end;

end.