class1.cs

来自DoFactory的设计模式, 由于是本人根据已有代码创建,没有NETOptimized项

// Iterator pattern -- Structural example  

using System;
using System.Collections;

namespace DoFactory.GangOfFour.Iterator.Structural
{

    // MainApp test application 

    class MainApp
    {
        static void Main()
        {
            ConcreteAggregate a = new ConcreteAggregate();
            a[0] = "Item A";
            a[1] = "Item B";
            a[2] = "Item C";
            a[3] = "Item D";

            // Create Iterator and provide aggregate 
            ConcreteIterator i = new ConcreteIterator(a);

            Console.WriteLine("Iterating over collection:");

            object item = i.First();
            while (item != null)
            {
                Console.WriteLine(item);
                item = i.Next();
            }

            // Wait for user 
            Console.Read();
        }
    }

    // "Aggregate" 

    abstract class Aggregate
    {
        public abstract Iterator CreateIterator();
    }

    // "ConcreteAggregate" 

    class ConcreteAggregate : Aggregate
    {
        private ArrayList items = new ArrayList();

        public override Iterator CreateIterator()
        {
            return new ConcreteIterator(this);
        }

        // Property 
        public int Count
        {
            get { return items.Count; }
        }

        // Indexer 
        public object this[int index]
        {
            get { return items[index]; }
            set { items.Insert(index, value); }
        }
    }

    // "Iterator" 

    abstract class Iterator
    {
        public abstract object First();
        public abstract object Next();
        public abstract bool IsDone();
        public abstract object CurrentItem();
    }

    // "ConcreteIterator" 

    class ConcreteIterator : Iterator
    {
        private ConcreteAggregate aggregate;
        private int current = 0;

        // Constructor 
        public ConcreteIterator(ConcreteAggregate aggregate)
        {
            this.aggregate = aggregate;
        }

        public override object First()
        {
            return aggregate[0];
        }

        public override object Next()
        {
            object ret = null;
            if (current < aggregate.Count - 1)
            {
                ret = aggregate[++current];
            }

            return ret;
        }

        public override object CurrentItem()
        {
            return aggregate[current];
        }

        public override bool IsDone()
        {
            return current >= aggregate.Count ? true : false;
        }
    }
}