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 。
源码 :
迭代器抽象类
abstract class Iteraor
{
public abstract object First();
public abstract object Next();
public abstract bool IsDone();
public abstract object CurrentItem();
}
聚集抽象类
abstract class Aggregate
{
public abstract Iterator CreateIterator();
}
//具体迭代器类 , 继承 Iterator
class ConcreteIterator : Iterator
{
private ConcreteAggregate aggregate ; 定义了一个具体聚集对象
private int current = 0;
public ConcreteIterator(ConcreteAggregate aggregate)
{
this.aggregate = aggregate;
}
public override object First()
{
return aggregate[0];
}
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];
}
}
//具体聚集类 , 继承 Aggregate
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.Inser(index,value); }
}
}
//客户端代码
static void Main(string[] args)
{
ConcreteAggregate a = new ConcreteAggregate();
a[0] = "大鸟";
a[1] = "小菜";
a[2] = "行李";
a[3] = "老外";
a[4] = "公交内部员工";
a[5] = "小偷";
Iterator i = new ConcreteIterator(a);
object item = i.First();
while(!i.IsDone())
{
Console.WriteLine("{0} 请买车票",i.CurrentItem());
i.Next();
}
Console.Read();
}
.NET 实现迭代器模式 : foreach in 语句