>>返回《C#常用設(shè)計(jì)模式》

• 1. 簡介
• 2. 示例

1. 簡介

把方法調(diào)用封裝起來: 通過封裝方法調(diào)用，可以把運(yùn)算塊封裝成形，所以調(diào)用此運(yùn)算對(duì)象不需要知道事情是如何進(jìn)行的。通過封裝方法調(diào)用，可以實(shí)現(xiàn)一些很聰明的事，比如日志記錄。

• 類圖
  
  其中提到的一個(gè)Command，可能為多個(gè)
• 日志的封裝
  • Ilogger就是Invoker
  • ILogger中的info、warn等方法就是執(zhí)行的Command
  • Receiver就是對(duì)應(yīng)：FileWriter、DBWriter

2. 示例

//遙控器 Invoker
public class RemoteControl
{
    private readonly ICommand _onCommand;
    private readonly ICommand _offCommand;

    public RemoteControl()
    {
        var noCommand = new NoCommand();
        _onCommands = noCommand;
        _offCommands = noCommand;
    }

    public void SetCommand(ICommand onCommand, ICommand offCommand)
    {
        _onCommand = onCommand;
        _offCommand = offCommand;
    }

    public void OnButtonWasPushed()
    {
        _onCommand.Execute();
    }

    public void OffButtonWasPushed()
    {
        _offCommand.Execute();
    }
}

//Command
public interface ICommand
{
    void Execute();
    void Undo();
}

//NoCommand對(duì)象是一個(gè)空對(duì)象，當(dāng)你不想返回一個(gè)有意義的對(duì)象時(shí)，空對(duì)象就很有用
public class NoCommand : ICommand
{
    public void Execute()
    {
        Console.WriteLine("No command was executed!");
    }
    public void Undo()
    {
        Console.WriteLine("No command was executed!");
    }
}

//ConcreteCommand
public class LightOffCommand : ICommand
{
    private readonly Light _light;

    public LightOffCommand(Light light)
    {
        _light = light;
    }

    public void Execute()
    {
        _light.Off();
    }

    public void Undo()
    {
        _light.On();
    }
}
public class LightOnCommand : ICommand
{
    private readonly Light _light;//這個(gè)字段就是ConcreteCommand中的一個(gè)Receiver，多用組合少用繼承！

    public LightOnCommand(Light light)
    {
        _light = light;
    }

    public void Execute()
    {
        _light.On();
    }

    public void Undo()
    {
        _light.Off();
    }
}

//Receiver
public class Light
{
    public void On()
    {
        Console.WriteLine("light's on");
    }

    public void Off()
    {
        Console.WriteLine("light's off");
    }
}

class Program
{
    static void Main(string[] args)
    {
        var control = new RemoteControl();
        var light = new Light();
        var lightOnCommand = new LightOnCommand(light);
        var lightOffCommand = new LightOffCommand(light);

        control.SetCommand(lightOnCommand, lightOffCommand);
        control.OnButtonWasPushed();
        Console.ReadKey();
    }
}