Head First 設計模式之命令模式（CommandPattern）

時間 2019-11-06

標籤 head 設計模式命令 commandpattern 简体版

原文原文鏈接

前言：

本章會將封裝帶入到一個全新的境界，把方法調用封裝起來。經過封裝方法調用，把運算塊包裝成形。調用此運算的對象不須要知道事情是如何進行的，只要知道如何使用包裝造成的方法來完成它就ok了。編程

1 現實場景應用

如今有一個遙控器，該遙控器有7個插槽須要編程，能夠在每一個插槽上放上不一樣的裝置，而後用按鈕控制它，這七個插槽具有各自的「開」「關」按鈕，還有一個總體用的撤銷按鈕，會撤銷最後一個按鈕的動做。數組

1.1 建立第一個命令對象

1.1.1 定義命令接口

public interfaceCommand
    {
        void Execute();
    }

1.1.2 實現一個打開燈的命令

publicclass Light //電燈類
    {
        public void On()
        {
            System.Console.WriteLine("Light  is On !");
        }
        public void Off()
        {
            System.Console.WriteLine("Light is Off !");
        }
}
    public class LightOnCommand : Command//實現開燈命令
    {
        private Light light;
        public LightOnCommand(Light light)
        {
            this.light = light;
        }
        public void Execute()
        {
            light.On();
        }      
    }

1.1.3 使用命令對象

public class LightControl
    {
        privateCommand soft;
        publicvoid SetCommand(Command cmd)
        {
            soft= cmd;//設置命令對象
        }
        publicvoid ButtonWasPressed()
        {
           soft.Execute();//調用命令對象的方法
        }
}

1.1.4 簡單測試

LightControl lightControl = new LightControl();//模擬命令的調用者
Lightlight = new Light();//建立一個電燈對象，做爲命令的接收者
LightOnCommand lightOnCommand = new LightOnCommand(light);//建立一個命令，並將接受者傳遞給它
lightControl.SetCommand(lightOnCommand);//將命令傳給調用者
lightControl.ButtonWasPressed();//模擬觸發按鈕

1.2 實現遙控器

public class RemoteControl
    {
        Command[] onCommands;//定義打開的命令數組
        Command[] offCommands; //定義關閉的命令數組
        public RemoteControl()
        {
            onCommands = new Command[7];
            offCommands = new Command[7];
            Command noCommand = newNoCommand();
            for (int i = 0; i < 7; i++)
            {
                onCommands[i] = noCommand;//初始化命令數組（默認設置爲無命令）
                offCommands[i] = noCommand;
            }
        }
        //將命令設置到對應的控制器
        public void SetCommand(int index,Command onCommand, Command offCommand)
        {
            onCommands[index] = onCommand;
            offCommands[index] = offCommand;
        }
        //觸發打開控制器
        public void OnButtonWasPressed(int index)
        {
            onCommands[index].Execute();
        }
        //觸發關閉控制器
        public void OffButtonWasPressed(intindex)
        {
            offCommands[index].Execute();
        }
        public override string ToString()
        {
            StringBuilder str = newStringBuilder();
            str.Append("\n------RemoteControl ------\n");
            for (int i = 0; i <onCommands.Length; i++)
            {
                str.Append("[solt" +i + "]" + onCommands[i].GetType().FullName + "      " +offCommands[i].GetType().FullName + "\n");
            }
            return str.ToString();
        }
    }

1.3 實現其餘控制器

 //關閉電燈命令
   public classLightOffCommand : Command
    {
        privateLight light;
        publicLightOffCommand(Light light)
        {
           this.light = light;
        }
        publicvoid Execute()
        {
           light.Off();
        }
        publicvoid Undo()
        {
           light.On();
        }
}
//打開電扇命令
public class CeilingFanOnCommand : Command
    {
       CeilingFan ceilingFan;
        intpreSpeed;
        publicCeilingFanOnCommand(CeilingFan ceilingFan)
        {
           this.ceilingFan = ceilingFan;
        }
        publicvoid Execute()
        {
           ceilingFan.On();
        }
        publicvoid Undo()
        {
           ceilingFan.Off();
        }
    }
 //關閉電扇命令
    public classCeilingFanOffCommand : Command
    {
       CeilingFan ceilingFan;
        publicCeilingFanOffCommand(CeilingFan ceilingFan)
        {
           this.ceilingFan = ceilingFan;
        }
        publicvoid Execute()
        {
           ceilingFan.Off();
        }
        publicvoid Undo()
        {
           ceilingFan.On();
        }
    }
//打開車庫門命令
    public classGarageDoorOnCommand : Command
    {
       GarageDoor garageDoor;
        publicGarageDoorOnCommand(GarageDoor garageDoor)
        {
            this.garageDoor= garageDoor;
        }
        publicvoid Execute()
        {
           garageDoor.On();
        }
        publicvoid Undo()
        {
           garageDoor.Off();
        }
    }
//關閉車庫門命令
    public classGarageDoorOffCommand : Command
    {
       GarageDoor garageDoor;
        publicGarageDoorOffCommand(GarageDoor garageDoor)
        {
           this.garageDoor = garageDoor;
        }
        publicvoid Execute()
        {
            garageDoor.Off();
        }
        publicvoid Undo()
        {
           garageDoor.On();
        }
    }
//打開CD命令
    public classStereCDOnCommand : Command
    {
        StereCDstereCD;
        publicStereCDOnCommand(StereCD stereCD)
        {
           this.stereCD = stereCD;
        }
 
        publicvoid Execute()
        {
           stereCD.On();
        }
        publicvoid Undo()
        {
           stereCD.Off();
        }
    }
//關閉CD命令
    public classStereCDOffCommand : Command
    {
        StereCDstereCD;
        publicStereCDOffCommand(StereCD stereCD)
        {
           this.stereCD = stereCD;
        }
        publicvoid Execute()
        {
           stereCD.Off();
        }
        publicvoid Undo()
        {
           stereCD.On();
        }
    }

1.4簡單測試

RemoteControlremoteControl = new RemoteControl ();
            CeilingFan ceilingFan = newCeilingFan("Living Room");//建立電扇對象
            GarageDoor garageDoor = newGarageDoor();//建立車庫門對象
            StereCD stereCD = new StereCD();//建立CD對象
Light light = new Light();//建立電燈對象
            LightOnCommand lightOnCommand = newLightOnCommand(light);//建立開燈命令
            LightOffCommand lightOffCommand =new LightOffCommand(light); //建立關燈命令
CeilingFanOnCommandceilingFanOn = new CeilingFanOnCommand(ceilingFan); //建立開電扇命令
            CeilingFanOffCommand ceilingFanOff= new CeilingFanOffCommand(ceilingFan);//建立關電扇命令
            GarageDoorOnCommand garageDoorOn =new GarageDoorOnCommand(garageDoor);//建立打開電扇命令
            GarageDoorOffCommand garageDoorOff= new GarageDoorOffCommand(garageDoor);//建立關閉電扇命令
            StereCDOnCommand stereCDOn = newStereCDOnCommand(stereCD);//建立打開CD命令
            StereCDOffCommand stereCDOff = newStereCDOffCommand(stereCD);//建立關閉CD命令
            remoteControl.SetCommand(0,lightOnCommand, lightOffCommand);//將電燈命令設置到對應的控制器上
            remoteControl.SetCommand(1,ceilingFanOn, ceilingFanOff); //將電燈命令設置到對應的控制器上
            remoteControl.SetCommand(2,garageDoorOn, garageDoorOff); //將車庫門命令設置到對應的控制器上
            remoteControl.SetCommand(3,stereCDOn, stereCDOff); //將CD命令設置到對應的控制器上
  remoteControl.OnButtonWasPressed(0);
           remoteControl.OffButtonWasPressed(0);
           remoteControl.OnButtonWasPressed(1);
           remoteControl.OffButtonWasPressed(1);
           remoteControl.OnButtonWasPressed(2);
           remoteControl.OffButtonWasPressed(2);
           remoteControl.OnButtonWasPressed(3);
           remoteControl.OffButtonWasPressed(3);

1.5 實現撤銷命令

1.5.1 修改命令接口，新增Undo（）方法

public interfaceCommand
    {
        void Execute();
        void Undo();//新增撤銷方法
}

1.5.2 修改命令，實現Undo方法

public class LightOnCommand : Command
    {
        private Light light;
        public LightOnCommand(Light light)
        {
            this.light = light;
        }
        public void Execute()
        {
            light.On();
        }
        public void Undo()//實現Undo方法
        {
            light.Off(); 
        }
}

其餘類都依次修改數據結構

1.5.3 修改RemoteControl類，新增Command對象記錄上一步操做

public class RemoteControlWithUndo
    {
       Command[] onCommands;
       Command[] offCommands;
        CommandundoCommand;//建立Command對象用來記錄上一步執行的命令
        publicRemoteControlWithUndo()
        {
           onCommands = new Command[7];
           offCommands = new Command[7];
           Command noCommand = new NoCommand();
            for(int i = 0; i < 7; i++)
            {
               onCommands[i] = noCommand;
               offCommands[i] = noCommand;
            }
           undoCommand = noCommand;
        }
………
……..
        publicvoid OnButtonWasPressed(int index)
        {
           onCommands[index].Execute();
           undoCommand = onCommands[index];//記錄打開命令
        }
        publicvoid OffButtonWasPressed(int index)
        {
           offCommands[index].Execute();
           undoCommand = offCommands[index];//記錄關閉命令
        }
        publicvoid UndoButtonWasPressed()//執行撤銷
        {
           undoCommand.Undo();
        }
       ……
       ……       
    }

1.6 宏命令

讓遙控器具備Party模式，即一個按鍵可以同步調用多個命令，這就是所謂的宏命令。ide

 public class MacroCommand : Command
    {
        Command[] commands;//定義命令數組，用來接收傳入的命令
        public MacroCommand(Command[] commands)
        {
            this.commands = commands;
        }
        public void Execute()//批量處理多個命令（即初始化的時候傳入的命令數組）
        {
            for (int i = 0; i <commands.Length; i++)
                commands[i].Execute();
        }
        public void Undo()
        {
            for (int i = 0; i <commands.Length; i++)
                commands[i].Undo();
        }
    }