Delphi 设计模式：《HeadFirst设计模式》Delphi7代码

命令模式可以很轻松的实现撤销（Undo）功能。
1. 命令的接受者
unit uReceiveObject;

interface

type
TLight = class(TObject)
public
procedure Open;
procedure Off;
end;

implementation

{ TLight }

procedure TLight.Off;
begin
Writeln('Light is off.');
end;

procedure TLight.Open;
begin
Writeln('Light is on.');
end;

end.


2.命令对象
unit uReceiveObject;

interface

type
TLight = class(TObject)
public
procedure Open;
procedure Off;
end;

implementation

{ TLight }

procedure TLight.Off;
begin
Writeln('Light is off.');
end;

procedure TLight.Open;
begin
Writeln('Light is on.');
end;

end.


 
3.命令的请求者
unit uSimpleRemoteWithUndo;

interface

uses
uCommandObject;

type
TSimpleRemoteWithUndo = class(TObject)
private
FOnCommand : TCommand;
FOffCommand : TCommand;
FUndoCommand: TCommand;
public
procedure SetCommand(aOnCommand, aOffCommand: TCommand);
procedure OnButtonWasPressed;
procedure OffButtonWasPressed;
procedure UndoButtonWasPressed;
end;

implementation

{ TSimpleRemoteWithUndo }

procedure TSimpleRemoteWithUndo.OffButtonWasPressed;
begin
FOffCommand.Execute;
FUndoCommand := FOffCommand;
end;

procedure TSimpleRemoteWithUndo.OnButtonWasPressed;
begin
FOnCommand.Execute;
FUndoCommand := FOnCommand;
end;

procedure TSimpleRemoteWithUndo.SetCommand(aOnCommand, aOffCommand: TCommand);
begin
FOnCommand := aOnCommand;
FOffCommand := aOffCommand;
end;

procedure TSimpleRemoteWithUndo.UndoButtonWasPressed;
begin
FUndoCommand.Undo;
end;

end.


 
4.客户端，创建具体的命令
program pSimpleRemoteWithUndoTest;

{$APPTYPE CONSOLE}

uses
uSimpleRemoteWithUndo in 'uSimpleRemoteWithUndo.pas',
uCommandObject in 'uCommandObject.pas',
uReceiveObje