这个例子还是比较好理解的， 所以只给出代码.

unit pattern;

interface

uses Dialogs;

type
TAudioPlayer = class;

TCommand = class
public
procedure execute; virtual; abstract;
end;

TPlayCommand = class(TCommand)
private
AudioPlayer: TAudioPlayer;
public
procedure execute; override;
procedure Playcommand(AP: TAudioPlayer);
end;

TStopCommand = class(TCommand)
private
AudioPlayer: TAudioPlayer;
public
procedure execute; override;
procedure StopComman(AP: TAudioPlayer);
end;

TRewindCommand = class(TCommand)
private
AudioPlayer: TAudioPlayer;
public
procedure execute; override;
procedure RewindCommand(AP: TAudioPlayer);
end;

TKeyPad = class
private
PlayCommand: TCommand;
StopCommand: TCommand;
RewindCommand: TCommand;
public
constructor Create(PlayC, StopC, RewindC: TCommand); virtual;
procedure play();
procedure stop();
procedure rewind();
end;

TAudioPlayer = class
public
procedure play();
procedure stop();
procedure rewind();
end;

TClient = class
private
KeyPad: TKeyPad;
AudioPlayer: TAudioPlayer;
public
constructor Create();
procedure test();
end;

implementation

{ TKeyPad }

constructor TKeyPad.Create(PlayC, StopC, RewindC: TCommand);
begin
PlayCommand := PlayC;
StopCommand := StopC;
RewindCommand := RewindC;
end;

procedure TKeyPad.play;
begin
PlayCommand.execute;
end;

procedure TKeyPad.rewind;
begin
RewindCommand.execute;
end;

procedure TKeyPad.stop;
begin
StopCommand.execute;
end;

{ TAudioPlayer }

procedure TAudioPlayer.play;
begin
ShowMessage('play');
end;

procedure TAudioPlayer.rewind;
begin
ShowMessage('rewind');
end;

procedure TAudioPlayer.stop;
begin
ShowMessage('stop');
end;

{ TPlayCommand }

procedure TPlayCommand.execute;
begin
inherited;
AudioPlayer.play();
end;

procedure TPlayCommand.Playcommand(AP: TAudioPlayer);
begin
self.AudioPlayer := AP;
end;

{ TRewindCommand }

procedure TRewindCommand.execute;
begin
inherited;
AudioPlayer.Rewind;
end;

procedure TRewindCommand.RewindCommand(AP: TAudioPlayer);
begin
AudioPlayer := ap;
end;

{ TStopCommand }

procedure TStopCommand.execute;
begin
inherited;
AudioPlayer.Stop;
end;

procedure TStopCommand.StopComman(AP: TAudioPlayer);
begin
AudioPlayer := ap;
end;

{ TClient }

constructor TClient.Create;
begin
AudioPlayer := TAudioPlayer.Create();
end;

procedure TClient.test;
var
PlayCommand: TCommand;
StopCommand: TCommand;
RewindCommand: TCommand;
begin
PlayCommand := TPlayCommand.Create;
StopCommand := TStopCommand.Create;
RewindCommand := TRewindCommand.Create;
KeyPad := TKeyPad.Create(PlayCommand, StopCommand, RewindCommand);
KeyPad.stop;
KeyPad.play;
KeyPad.rewind;
KeyPad.Stop;
end;

end.