设计模式之迭代器模式

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说起迭代器，大家一定不陌生，经常使用的foreach in 这种循环就是，C#语言已经内置化了迭代器模式，主要是支持对非泛型集合的简单迭代接口IEumerator和公开枚举数IEnumerable。虽然内置了，但是这种模式也有我们学习的必要性。

代码如下

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace 设计模式之迭代器模式{    public abstract class Iterator//抽象迭代器    {        public abstract object First();        public abstract object Next();        public abstract object Current();        public abstract bool IsMax();    }    public abstract class Aggregate//抽象被迭代的对象    {        public abstract Iterator CreateIterator();    }    public class AIterator : Iterator//具体的迭代器    {        public AAggregate listA = new AAggregate();//存放被迭代的对象        private int current=0;        public AIterator(AAggregate a)//初始化时绑定被迭代的对象        {            listA = a;        }        public override object First()//获得第一个迭代的对象        {            return listA[0];        }        public override object Next()//获得当前对象的下一个对象        {            current++;            if (current < listA.Count())            {                return listA[current];            }            else            {                return null;            }        }        public override object Current()//获得当前对象        {            return listA[current];        }        public override bool IsMax()        {            return current == listA.Count() ? true : false;        }    }    public class AAggregate : Aggregate//具体的被迭代对象，迭代方向是正向。    {        public IList<object> lists = new List<object>();        public override Iterator CreateIterator()//创被迭代对象的造迭代器        {            return new AIterator(this);        }        public int Count()//获得被迭代对象的个数        {            return lists.Count;        }        public object this[int index]//索引器        {            get            {                return lists[index];            }            set            {                lists.Insert(index, value);            }        }    }    public class BIterator : Iterator    {        public AAggregate blist = new AAggregate();        private int current=0;        public BIterator(AAggregate a)        {            blist = a;            current = a.Count() - 1;        }        public override object Current()        {            return blist[current];        }        public override object First()        {            return blist[blist.Count()-1];        }        public override bool IsMax()        {            return current<0? true : false;        }        public override object Next()        {            current--;            if(current>=0)            {                return blist[current];            }            return null;        }    }    class Program    {        static void Main(string[] args)        {            AAggregate a = new AAggregate();            a[0] = "你好";            a[1] = "你真的好吗？";            a[2] = "你他妈有病啊！老子很好";            AIterator b = new AIterator(a);            while(!b.IsMax())            {                Console.WriteLine(b.Current());                b.Next();            }            Console.WriteLine();            BIterator c = new BIterator(a);            while(!c.IsMax())            {                Console.WriteLine(c.Current());                c.Next();            }            Console.Read();        }    }}

运行结果：

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