设计模式:迭代器模式
迭代器模式(Iterator):提供一种方法顺序访问一个聚合对象中各个元素,而又不暴露该对象的内部表示。
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namespace IteratorDesign { public abstract class Iterator { public abstract object First(); public abstract object Next(); public abstract bool IsDone(); public abstract object CurrentItem(); } public abstract class Aggregate { public abstract Iterator CreateIterator(); } public class ConcreteAggregate : Aggregate { private IList<object> items = new List<object>(); public override Iterator CreateIterator() { return new ConcreteIterator(this); } public int Count { get { return items.Count; } } public object this[int index] { get { return items[index]; } set { items.Insert(index, value); } } } public class ConcreteIterator : Iterator { private ConcreteAggregate aggregate; private int current = 0; public ConcreteIterator(ConcreteAggregate aggregate) { this.aggregate = aggregate; } public override object CurrentItem() { return aggregate[current]; } public override object First() { return aggregate[0]; } public override bool IsDone() { return current >= aggregate.Count ? true : false; } public override object Next() { object ret = null; current++; if(current<aggregate.Count) { ret = aggregate[current]; } return ret; } } }
测试代码:
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ConcreteAggregate a = new ConcreteAggregate(); a[0] = "A"; a[1] = "B"; a[2] = "C"; Iterator i = new ConcreteIterator(a); object item = i.First(); while(!i.IsDone()) { Console.WriteLine(i.CurrentItem()); i.Next(); }