设计模式-迭代器模式

interface Iterator
    {
        object First();
        object Next();
        bool isDone();
        object CurrentItem();
    }
    class myIterator : Iterator
    {
        private MyAggragate items;
        private int cuttent = 0;
        public myIterator(MyAggragate _items)
        {
            items = _items;
        }
        public object CurrentItem()
        {            
            return items[cuttent];
        }

        public object First()
        {
            return items[0];
        }

        public bool isDone()
        {
            return cuttent>=items.Count?true:false;
        }

        public object Next()
        {
            cuttent++;
            if (cuttent >= items.Count)
                return null;
            return items[cuttent];
        }
    }

        abstract class Aggragate
    {
        public abstract Iterator CreateIterator();
    }
    class MyAggragate : Aggragate
    {
        private IList<string> list = new List<string>();

        public int Count
        {
           get
            {
                return list.Count;
            }
        }
        public string this[int index]
        {
            get
            {
                return list[index];
            }
            set
            {
                list.Insert(index, value);
            }
        }
        public override Iterator CreateIterator()
        {
            return new myIterator(this);
        }
    }

        //前端
        static void Main(string[] args)
        {
            MyAggragate a = new MyAggragate();
            a[0] = "张三";
            a[1] = "李四";
            a[2] = "王五";
            a[3] = "王五2";
            diedaiqi.Iterator i = new myIterator(a);
            var item = i.First();
            Console.WriteLine("{0}1", item);
            while (!i.isDone())
            {
                Console.WriteLine("{0}",i.CurrentItem());
                i.Next();
            }
            Console.ReadLine();
        }

总结：访问聚集对象，不管该对象是什么，需要遍历的时候，就使用迭代器。
迭代器模式：为聚集提供开始、下一个、是否结束、当前处于哪一项的统一的接口。
C#的集合什么的已经在内部实现了迭代器。
foreach(string item in a)
{
console.write("当前{0}",item);
}的内部实现其实是：
IEnumerator<string> e=a.GetEnumerator();
while(e.Next())
{
console.write("当前{0}",e.Current);
}