设计模式面对面之命令模式

Posted 2020-10-14

命令模式

类图：

 

常用的实现方式：

 指令处理对象

public interface IReceiver  {

        void Operation();
    }//end IReceiver

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public class ReceiverA : IReceiver {

        public ReceiverA(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverA处理");
        }

    }//end ReceiverA

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public class ReceiverB : IReceiver {

        public ReceiverB(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverB处理");
        }

    }//end ReceiverB

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指令对象

public interface ICommand  {

        void Execute();
    }//end ICommand

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public class CommandRealizeA : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeA(){
            _receiver=new ReceiverA();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeA

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public class CommandRealizeB : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeB()
        {
            _receiver=new ReceiverB();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeB

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调用对象

public class Invoker {

        private ICommand _command;

        public Invoker(){
            _command=new CommandRealizeA();//默认指令
        }

        public void Invoke()
        {
            _command.Execute();
        }

        /// 
        /// <param name="command"></param>
        public void SetCommand(ICommand command)
        {
            _command = command;
        }

    }//end Invoker

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 使用场景：

 当每次请求或者动作会出现一连串操作,此时可以考虑。比如提交表单后台涉及到数据库操作，日志操作，缓存操作等等，这些操作可以用命令模式去控制。

 命令模式将命令的调用者（发出者），执行者，处理着，从一个紧耦合的动作，分离开来，主要用来复杂的动作解耦和指令（命令）管理。