设计模式-迭代器模式

学习其实现方式

迭代器模式

//Iterator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();
}
//具体迭代器类
class ConcreateIterator : Iterator
{
    private ConcreateAggregate aggregate;
    private int current = 0;
    public ConcreateIterator(ConcreateAggregate aggregate)
    {
        this.aggregate = aggregate;
    }
    public override object First()
    {
        return this.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;
    }
    public override object CurrentItem()
    {
        return aggrate[current];
    }

}
//抽象聚集类
abstract class Aggregate
{    
    public abstract Iterator CreateIterator();//创建迭代器
}
//具体聚集类
class ConcreateAggregate : Aggregate
{
    private IList<object> items new List<object>();
    public override Iterator CreateIterator()
    {
        return new ConcreateIterator(this);
    }
    public int Count
    {get { return items.Count;} }
    public object this[int index]
    {
        get{return items[index];}
        set{items.Insert(index, value);}
    }
}
//Client
ConcreateAggregate ca = new ConcreateAggregate();
ca[0] = "0";
ca[1] = "1";
ca[2] = "2";
Iterator i = new ConcreateIterator(ca);
object item = i.First();
while(!i.IsDone)
{
    Console.WriteLine(i.CurrentItem());
    i.Next();
}