命令模式是对命令的封装.命令模式把发出命令的责任和执行命令的责任分割开,委派给不同的对象.该模式的示意类图如下:
![](/images/cnblogs_com/dotnetfresh/command.jpg)
下面是一个Command模式的例子(模仿<Java与模式>中的例子).
现有一个录音机(AudioPlayer),他有播放(Play),到带(Rewind)和停止(Stop)三个功能,利用Command模式实现中,录音机(AudioPlayer)则为Receiver对象,将录音机的键盘作为Invoker对象,因为客户是通过他去执行播放,倒带,停止的功能(命令).
首先:定义录音机对象
/// <summary>
/// 录音机对象,该对象充当Receiver角色
/// </summary>
public class AudioPlayer
{
public AudioPlayer()
{
}
![](/Images/OutliningIndicators/InBlock.gif)
/// <summary>
/// 播放
/// </summary>
public void Play()
{
Console.WriteLine("Playing
");
}
![](/Images/OutliningIndicators/InBlock.gif)
/// <summary>
/// 停止
/// </summary>
public void Stop()
{
Console.WriteLine("Stoping
");
}
![](/Images/OutliningIndicators/InBlock.gif)
/// <summary>
/// 倒带
/// </summary>
public void Rewind()
{
Console.WriteLine("Rewinding
");
}
}接下来定义命令对象,在这里,我采用一个抽象类AbstractCommand(ICommand角色)做为所有具体命令类的父类,所有具体命令类都要继承自该抽象类:
public abstract class AbstractCommand
{
protected AudioPlayer _player;
public AbstractCommand(AudioPlayer player)
{
this._player = player;
}
![](/Images/OutliningIndicators/InBlock.gif)
public abstract void Execute();
}具体命令对象如下:
/// <summary>
/// 播放命令
/// </summary>
public class PlayCommand : AbstractCommand
{
public PlayCommand(AudioPlayer player) : base(player)
{
}
#region ICommand 成员
![](/Images/OutliningIndicators/InBlock.gif)
public override void Execute()
{
_player.Play();
}
![](/Images/OutliningIndicators/InBlock.gif)
#endregion
}
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/// <summary>
/// 停止命令
/// </summary>
public class StopCommand : AbstractCommand
{
public StopCommand(AudioPlayer player) : base(player)
{
}
#region ICommand 成员
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public override void Execute()
{
_player.Stop();
}
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#endregion
}
![](/Images/OutliningIndicators/None.gif)
/// <summary>
/// 倒带命令
/// </summary>
public class RewindCommand : AbstractCommand
{
public RewindCommand(AudioPlayer player) : base(player)
{
}
#region ICommand 成员
![](/Images/OutliningIndicators/InBlock.gif)
public override void Execute()
{
_player.Rewind();
}
![](/Images/OutliningIndicators/InBlock.gif)
#endregion
}接下来定义键盘对象KeyPad(Invoker角色):
/// <summary>
/// 录音机键盘对象,该对象充当Invoker角色
/// </summary>
public class KeyPad
{
private AbstractCommand _playCmd;
private AbstractCommand _stopCmd;
private AbstractCommand _rewindCmd;
![](/Images/OutliningIndicators/InBlock.gif)
public KeyPad(AbstractCommand playCmd,AbstractCommand stopCmd,AbstractCommand rewindCmd)
{
this._playCmd = playCmd;
this._stopCmd = stopCmd;
this._rewindCmd = rewindCmd;
}
![](/Images/OutliningIndicators/InBlock.gif)
public void Play()
{
_playCmd.Execute();
}
![](/Images/OutliningIndicators/InBlock.gif)
public void Stop()
{
_stopCmd.Execute();
}
![](/Images/OutliningIndicators/InBlock.gif)
public void Rewind()
{
_rewindCmd.Execute();
}
}现在,客户端就可以这样控制录音机了:
AudioPlayer player = new AudioPlayer(); //定义receiver对象
![](/Images/OutliningIndicators/None.gif)
/*各个具体命令对象*/
AbstractCommand playCmd = new PlayCommand(player);
AbstractCommand stopCmd = new StopCommand(player);
AbstractCommand rewindCmd = new RewindCommand(player);
![](/Images/OutliningIndicators/None.gif)
KeyPad pad = new KeyPad(playCmd,stopCmd,rewindCmd); //定义invoker对象
/*通过invoker进行命令的执行*/
pad.Play();
pad.Rewind();
pad.Stop();
![](/images/cnblogs_com/dotnetfresh/command.jpg)
下面是一个Command模式的例子(模仿<Java与模式>中的例子).
现有一个录音机(AudioPlayer),他有播放(Play),到带(Rewind)和停止(Stop)三个功能,利用Command模式实现中,录音机(AudioPlayer)则为Receiver对象,将录音机的键盘作为Invoker对象,因为客户是通过他去执行播放,倒带,停止的功能(命令).
首先:定义录音机对象
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