迭代器模式：
提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露该对象的内部表示。
C#/java中的foreach就是迭代器的使用。
.net
IEumerator支持对非泛型集合的简单迭代接口。
如foreach(string i in Str){print i}
就是：
IEnumerator<string>e=Str.GetEnumerator();
While(e.MoveNext())
{
Printe.Current;
}
Demo:
//迭代器抽象类
abstract class Iterator
{
public abstract object First();
public abstract object Next();
public abstract bool IsDone();
public abstract object CurrentItem();
}
//具体迭代器
class ConcreteIterator : Iterator
{
private ConcreteAggregate aggregate;
private int current = 0;
public ConcreteIterator(ConcreteAggregate aggregate)
{
this.aggregate = aggregate;
}
public override object First()
{
return aggregate;
}
public override object Next()
{
object ret = null;
current++;
if (current < aggregate.Count)
{
ret=aggregate[current];
}
return ret;
}
public override bool IsDone()
{
return current >= aggregate.Count ? true : false;
}
public override object CurrentItem()
{
return aggregate[current];
}
}
//聚集抽象类
abstract class Aggregate
{
public abstract Iterator CreateIterator();
}
//具体聚集类
class ConcreteAggregate : Aggregate
{
private IList<object> items=new List<object>();
public override Iterator CreateIterator()
{
return new ConcreteIterator(this);
}
public int Count//返回聚集总数
{
get { return items.Count; }
}
publicobject this[int index]//声明一个索引器
{
get { return items[index]; }
set { items.Insert(index,value ); }
}
}
class Program
{
static void Main(string[] args)
{
ConcreteAggregate a = new ConcreteAggregate();
a[0] = "大鸟";
a[1] = "大鸟1";
a[2] = "大鸟2";
a[3] = "大鸟3";
Iterator i = new ConcreteIterator(a);
//object ittem = i.First();
while (!i.IsDone())
{
Console.WriteLine("{0}请买票。",i.CurrentItem());
i.Next();
}
Console.ReadKey();
}
}