命令模式

模式定义

命令模式(Command Pattern)：将一个请求封装为一个对象，从而使我们可用不同的请求对客户进行参数化；对请求排队或者记录请求日志，以及支持可撤销的操作。

UML类图

• 抽象命令 Command
• 具体命令 ConcreteCommand
• 调用者 Invoker

• 接收者 Receiver

  代码结构

  public class CommandApp
  {
      public void Run()
      {
          Receiver receiver = new Receiver();
          Command command = new ConcreteCommand(receiver);
          Invoker invoker = new Invoker();
  
          invoker.SetCommand(command);
          invoker.ExecuteCommand();
          Console.ReadKey();
      }
  }
  
  /// <summary>
  /// 抽象命令
  /// </summary>
  abstract class Command
  {
      protected Receiver receiver;
  
      public Command(Receiver receiver)
      {
          this.receiver = receiver;
      }
  
      public abstract void Execute();
  }
  
  /// <summary>
  /// 具体命令
  /// </summary>
  class ConcreteCommand : Command
  {
      public ConcreteCommand(Receiver receiver) : base(receiver)
      {
      }
  
      public override void Execute()
      {
          receiver.Action();
      }
  }
  
  /// <summary>
  /// 接收者
  /// </summary>
  class Receiver
  {
      public void Action()
      {
          Console.WriteLine("Called Receiver.Action()");
      }
  }
  
  /// <summary>
  /// 调用者
  /// </summary>
  class Invoker
  {
      private Command _command;
  
      public void SetCommand(Command command)
      {
          this._command = command;
      }
  
      public void ExecuteCommand()
      {
          _command.Execute();
      }
  }

情景案例

电视机遥控器例子，电视器Receiver 遥控器Invoker

public class User
    {
        public void Use()
        {
            TV tv = new TV();
            Command command = new ConcreteCommand(tv);
            RemoteControl remote = new RemoteControl();

            remote.SetCommand(command);

            remote.SetChannel(50);
            tv.Display();

            remote.DownChannel();
            remote.UpSound();
            tv.Display();

            Console.ReadKey();
        }
    }

    /// <summary>
    /// 抽象命令
    /// </summary>
    abstract class Command
    {
        protected TV tv;

        public Command(TV tv)
        {
            this.tv = tv;
        }
        /// <summary>
        /// 设置音量
        /// </summary>
        /// <param name="n"></param>
        public abstract void SetSound(int n);

        /// <summary>
        /// 设置频道
        /// </summary>
        /// <param name="n"></param>
        public abstract void SetChannel(int n);
    }

    /// <summary>
    /// 具体命令
    /// </summary>
    class ConcreteCommand : Command
    {
        public ConcreteCommand(TV tv) : base(tv)
        {
        }

        public override void SetChannel(int n)
        {
            this.tv.SetChannel(n);
        }

        public override void SetSound(int n)
        {
            this.tv.SetSound(n);
        }
    }

    /// <summary>
    /// 电视机
    /// </summary>
    class TV
    {
        private int _sound = 0;
        private int _channel = 0;

        public void SetSound(int n)
        {
            _sound = n;
        }

        public void SetChannel(int n)
        {
            _channel = n;
        }

        public void Display()
        {
            Console.WriteLine("现在电视的频道是：{0}，音量是：{1}", _channel, _sound);
        }
    }

    /// <summary>
    /// 遥控器
    /// </summary>
    class RemoteControl
    {
        private int _sound=0;
        private int _channel=0;

        /// <summary>
        /// 最多有99个频道
        /// </summary>
        private int _maxChannel = 99;

        /// <summary>
        /// 音量最大100
        /// </summary>
        private int _maxSound = 100;

        private Command _command;

        public void SetCommand(Command command)
        {
            this._command = command;
        }

        /// <summary>
        /// 直接按数字输入频道
        /// </summary>
        /// <param name="n"></param>
        public void SetChannel(int n)
        {
            if (n >= 0 && n <= _maxChannel)
            {
                _channel = n;
                this._command.SetChannel(n);
            }
        }

        public void UpSound()
        {
            if(_sound < _maxSound)
            {
                _sound++;
            }
            this.SetSound(_sound);
        }

        public void DownSound()
        {
            if (_sound > 0)
            {
                _sound--;
            }
            this.SetSound(_sound);
        }

        public void UpChannel()
        {
            if (_channel < _maxChannel)
            {
                _channel++;
            }
            else
            {
                _channel = 0;
            }
            this.SetChannel(_channel);
        }

        public void DownChannel()
        {
            if (_channel > 0)
            {
                _channel--;
            }
            else
            {
                _channel = _maxChannel;
            }
            this.SetChannel(_channel);
        }

        private void SetSound(int n)
        {
            if(n>=0 && n<= _maxSound)
            {
                _sound = n;
                this._command.SetSound(_sound);
            }
        }
    }