设计模式学习笔记——迭代器模式（Iterator）

1.特点：将对集合的访问与遍历从集合对象中分离出来到迭代器中。

2.概念：迭代器模式（Iterator）就是分离了聚合对象的遍历行为，抽象出一个迭代器来负责这样既可以做到不暴露集合的内部结构，又可让外部代码透明的访问集合内部数据。

3.类图：

4.程序实现

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// 抽象聚合类
    public interface IListCollection
    {
        Iterator GetIterator();
    }
  
     
// 迭代器抽象类
    public interface Iterator
    {
        bool MoveNext();
        Object GetCurrent();
        void Next();
        void Reset();
    }
  
     
// 具体聚合类
    public class ConcreteList : IListCollection
    {
        int[] collection;
        public ConcreteList()
        {
            collection = new int[] { 2, 4, 6, 8 };
        }
  
        public Iterator GetIterator()
        {
            return new ConcreteIterator(this);
        }
  
        public int Length
        {
            get { return collection.Length; }
        }
  
        public int GetElement(int index)
        {
            return collection[index];
        }
    }
  
     
// 具体迭代器类
    public class ConcreteIterator : Iterator
    {
         
// 迭代器要集合对象进行遍历操作，自然就需要引用集合对象
        private ConcreteList _list;
        private int _index;
  
        public ConcreteIterator(ConcreteList list)
        {
            _list = list;
            _index = 0;
        }
  
        public bool MoveNext()
        {
            if (_index < _list.Length)
            {
                return true;
            }
            return false;
        }
  
        public Object GetCurrent()
        {
            return _list.GetElement(_index);
        }
  
        public void Reset()
        {
            _index = 0;
        }
  
        public void Next()
        {
            if (_index < _list.Length)
            {
                _index++;
            }
  
        }
    }
  
     
// 客户端
    class Program
    {
        static void Main(string[] args)
        {
            Iterator iterator;
            IListCollection list = new ConcreteList();
            iterator = list.GetIterator();
  
            while (iterator.MoveNext())
            {
                int i = (int)iterator.GetCurrent();
                Console.WriteLine(i.ToString());
                iterator.Next();
            }
  
            Console.Read();
        }
    }