转载猫来老鼠跑掉

C#委托探索之猫和老鼠

场景描述

猫和老鼠：猫来了，老鼠跑掉！怎么实现？

实现代码

之前实现方式：

public class Cat
     {
         
         public void ScreamOut(string msg)
         {
              mouse.RunAway();
         }
     }
     public class Mouse
     {
         
         public void RunAway()
          
 
     }

 

但是如果老鼠繁殖多了，很多老鼠同时都要跑掉，有的向南有的向北，怎么办呢？重写猫的ScreamOut 方法，这样显然不好；

现实中的情况是，每个老鼠听到猫来了这个情况，自己有自己的逃跑方式，于是委托用到了这里，即：委托相当于一个方法 但是它的参数也是一个方法，这就不能用一般的方法那样定义了；

委托实现如下：

猫类：

public class Cat
     {
         public string Name { get; set; }
         public delegate void ScreamEventHandler(object sender, ScreamEventArgs e);
         public event ScreamEventHandler Scream;
         public virtual void OnScream(ScreamEventArgs e)
         {
             if (this.Scream != null)
             {
                 this.Scream(this, e);
             }
         }
         public void ScreamOut(string msg)
         {
             ScreamEventArgs e = new ScreamEventArgs(msg);
             OnScream(e);
         }
     }

 

鼠类：

 public class Mouse
     {
         public string Name { get; set; }
         public Mouse(Cat cat)
         {
             cat.Scream += new Cat.ScreamEventHandler(cat_Scream);
             cat.Scream += this.RunAway;
         }
         public void RunAway(object sender, ScreamEventArgs e)
         {
             Cat c = (Cat)sender;
             Console.WriteLine("{0} coming,she said:\"{1}\",{2} running!(Running...)", c.Name, e.Msg, this.Name);
         }
         void cat_Scream(object sender, ScreamEventArgs e)
         {
             Cat c = (Cat)sender;
             Console.WriteLine("{0} coming,she said:\"{1}\",{2} running!", c.Name, e.Msg, this.Name);
         }
 
     }

这里的委托定义和.net Framework 类库定义方式相同，有助于了解系统提供的委托机制，所以还有一个猫叫事件的参数类：

public class ScreamEventArgs
     {
         public readonly string Msg;
         public ScreamEventArgs(string msg)
         {
             this.Msg = msg;
         }
     }

 

主类调用代码：

class Program
     {
         static void Main(string[] args)
         {
             Cat c1 = new Cat();
             c1.Name = "tom";
 
             Mouse m1 = new Mouse(c1);
             m1.Name = "Jearry";
 
             Mouse m2 = new Mouse(c1);
             m2.Name = "Jearry's son";
 
             c1.Scream += m2.RunAway;
 
             c1.ScreamOut("stop");
 
             Console.Read();
         }
     }

执行结果：

 

源文出自：http://www.cnblogs.com/mrzzcn/archive/2012/09/07/delegate.html