命令模式

命令模式，作用就是让行为和对象分离，这样可以方便地为对象扩展行为。

对文档的操作：

文档代码：

    public class Document
    {
        public string Title { get; set; }
        public string Content { get; set; }

        //public void Read()
        //{
        //    Console.WriteLine("Read ");
        //}
        //public void Write()
        //{
        //    Console.WriteLine("Write ");
        //}
    }

文档对象有两个行为，读和写。如果我要对文档的行为进行扩展，就必须要修改文档，这样违背了开闭原则。

我们把文档的对象和行为进行分离。

    public abstract class BaseReceiver
    {
        public abstract void Execute(Document doc);
    }

    public class ReadReceiver : BaseReceiver
    {
        public override void Execute(Document doc)
        {
            Console.WriteLine("Read：{0}，{1}", doc.Title, doc.Content);
        }
    }

    public class WriteReceiver : BaseReceiver
    {
        public override void Execute(Document doc)
        {
            Console.WriteLine("Write：{0}，{1}", doc.Title, doc.Content);
        }
    }

把读取和写入分别建做成不同的对象，进行单一职责的分离。

并且抽象出来，这样就支持灵活的扩展和修改，可以随意增加而不会影响其它任何原有的行为。

包装一层：

    public abstract class BaseCommand
    {
        public abstract void Execute(Document doc);
    }

    public class ReadCommand : BaseCommand
    {
        private BaseReceiver BaseReceiver = null;
        public ReadCommand(BaseReceiver baseReceiver)
        {
            BaseReceiver = baseReceiver;
        }

        public override void Execute(Document doc)
        {
            BaseReceiver.Execute(doc);
        }

    }

    public class WriteCommand : BaseCommand
    {
        private BaseReceiver BaseReceiver = null;
        public WriteCommand(BaseReceiver baseReceiver)
        {
            BaseReceiver = baseReceiver;
        }

        public override void Execute(Document doc)
        {
            BaseReceiver.Execute(doc);
        }
    }

这里面的作为，我也搞不懂。待续。

增加一个调用者：

    public class Invoker
    {
        private BaseCommand baseCommand = null;
        public Invoker(BaseCommand basecommand)
        {
            baseCommand = basecommand;
        }

        public void Execute(Document doc)
        {
            baseCommand.Execute(doc);
        }
    }

同样，待续。

 

使用：

 

   Document doc = new Document()
            {
                Title = "如梦令",
                Content = "昨夜雨疏风骤，浓睡不消残酒。试问卷帘人，却道“海棠依旧”。“知否？知否？应是绿肥红瘦。”"
            };

            Console.WriteLine("---行为和对象分离 Receiver---------------------------------");

            BaseReceiver write = new WriteReceiver();
            write.Execute(doc);

            BaseReceiver Read = new ReadReceiver();
            Read.Execute(doc);

            Console.WriteLine("---再包装一层 Command---------------------------------");

            BaseCommand writeCommand = new WriteCommand(write);
            writeCommand.Execute(doc);

            BaseCommand readCommand = new ReadCommand(Read);
            readCommand.Execute(doc);

            Console.WriteLine("---再包装一层 Invoker---------------------------------");

            Invoker writeinvoker = new Invoker(writeCommand);
            writeinvoker.Execute(doc);

            Invoker readinvoker = new Invoker(readCommand);
            readinvoker.Execute(doc);

            Console.ReadLine();

 

运行结果：