C#使用yield关键字构建迭代器详解

以前，如果我们希望构建支持foreach枚举的自定义集合，只能实现IEnumerable接口（可能还有IEnumerator()）,返回值还必须是IEnumerator类型，除此之外还可以通过迭代器来使用构建foreach循环的类型，详细见下链接。

 代码

public class Car
 {
   //内部状态数据
   public int CurentSpeed;
   public int MaxSpeed;
   public string name;
   //汽车能不能用
   private bool carIsdead;
   //类构造函数
   public Car() { }
   public Car(string name, int currentspeed, int maxspeed = 100)
   {
     this.name = name;
     this.CurentSpeed = currentspeed;
     this.MaxSpeed = maxspeed;
   }
   //定义委托类型
   public delegate void CarEngineHandler(string msdForCar);
   //定义每个委托类型的成员变量
   private CarEngineHandler listOfhandlers;
   //向调用者添加注册函数
   public void RegisterWithCarEngine(CarEngineHandler methodTocall)
   {
     if (listOfhandlers == null)
       listOfhandlers = methodTocall;
     else
       listOfhandlers += methodTocall;//支持多路广播
   }
   //实现Accelerate()方法
   public void Accelerate(int delta)
   {
     if (carIsdead)
     {
       if (listOfhandlers != null)
       {
         listOfhandlers("sorry,this car is dead");
       }
     }
     else
     {
       CurentSpeed += delta;
       //不能超过最大速度
       if (5 == (MaxSpeed - CurentSpeed) && listOfhandlers != null)
       {
         listOfhandlers("this speed is nearly to the maxspeed");
       }
       if (CurentSpeed > MaxSpeed)
       {
         carIsdead = true;
       }
       else
         Console.WriteLine("current speed:{0}", CurentSpeed);
     }
   }
 }
 public class Garage : IEnumerable
 {
   private Car[] garage = new Car[3];
   public Garage()
   {
     garage[0] = new Car("a", 10);
     garage[1] = new Car("b", 13);
     garage[2] = new Car("c", 14);
   }
   public Enumerator GetEnumerator()
   {
     //返回数组对象的IEnumerator
     //return garage.GetEnumerator();
     //用yield关键字构建迭代器方法
     foreach (Car c in garage)
     {
       //当yield return语句执行后，当前位会被
       //保存下来，下一次执行会从当前位开始
       yield return c;
     }
   }
 }
 class Program
 {
   static void Main(string[] args)
   {
     Garage g = new Garage();
     foreach (Car c in g)
     {
       Console.WriteLine("car name:{0}", c.name);
     }
   }
 }

参考：C#中可枚举类型详解

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。

原文链接：http://www.cnblogs.com/janghe/p/7454867.html