迭代器模式：对象索引器

1.迭代类的封装

namespace Data
{
    /*迭代器模式：仿照IEnumerator接口，实现一个简单的迭代器。*/

    //迭代器接口
    public interface IIterators
    {
        int currentIndexx { get; set; }
        object GetCurrentItem();
        object GetFirst();
        void Next();
        bool IsLast();
    }

    //具体实现
    public class Iterators : IIterators
    {
        /// <summary>
        /// 具体聚集对象
        /// </summary>
        private GatheredEx gatheredEx;

        private int currentIndex;

        /// <summary>
        /// 接口中的属性
        /// </summary>
        int IIterators.currentIndexx
        {
            get
            {
                return currentIndex;
            }
            set
            {
                currentIndex = value;
            }
        }

        /// <summary>
        /// 在构造函数中实例化未来要遍历集合中的元素
        /// </summary>
        /// <param name="gatheredExObj"></param>
        public Iterators(GatheredEx gatheredExObj)
        {
            gatheredEx = gatheredExObj;
        }
        #region IIterators 成员

        /// <summary>
        /// 得到当前对象
        /// </summary>
        /// <returns></returns>
        public object GetCurrentItem()
        {
            return gatheredEx[currentIndex];
        }

        /// <summary>
        /// 得到第一个对象
        /// </summary>
        /// <returns></returns>
        public object GetFirst()
        {
            return gatheredEx[0];
        }

        /// <summary>
        /// 修改索引值，以访问下一个对象
        /// </summary>
        /// <returns></returns>
        public void Next()
        {
            currentIndex++;
        }

        /// <summary>
        /// 是否为最后一个元素
        /// </summary>
        /// <returns></returns>
        public bool IsLast()
        {
            return currentIndex < gatheredEx.Count;
        }

        #endregion
    }

    //聚集对象，用来表示要遍历的数组或集合
    public abstract class Gathered
    {
        public abstract IIterators CreateIIterators();
    }

    //具体聚集类
    public class GatheredEx : Gathered
    {
        //存放要遍历的对象
        public IList<object> list = new List<object>();

        public override IIterators CreateIIterators()
        {
            return new Iterators(this);
        }

        //返回集合中元素个数
        public int Count { get { return list.Count; } }

        /// <summary>
        /// 定义索引器，允许对象可以按照数组的方式进行访问
        /// this 关键字用于定义索引器
        /// get 访问器返回值。set 访问器分配值
        /// value 关键字用于定义由 set 索引器分配的值
        /// 索引器的索引值并不一定非要整形，可根据自己的需求定义索引类型
        /// 索引器可以有多个形参，例如当访问二维数组时(MSDN)
        /// </summary>
        /// <param name="index"></param>
        /// <returns></returns>
        public object this[int index]
        {
            get { return list[index]; }
            set { list.Insert(index, value); }
        }
    }
}

2.调用

       static void Main(string[] args)
        {
            /* g[0] = "A"; 是object类型，所以，通过数组方式访问该对象可以
             * 为其赋任何类型的值*/

            GatheredEx g = new GatheredEx();
            g[0] = "A";
            g[1] = "B";
            g[2] = "C";
            g[3] = "D";
            g[4] = "E";

            //把以上对象存入迭代器
            IIterators it = new Iterators(g);
            Console.WriteLine("获取第一个值:{0}",it.GetFirst());
            while (it.IsLast())
            {
                Console.WriteLine("{0}为：{1}",it.currentIndexx,it.GetCurrentItem());
                it.Next();
            }

            Console.ReadKey();
        }