iteratorrealworld.cs

使用C#程序将23个常用设计模式进行列表显示

using System;
using System.Windows.Forms;
using System.Collections;

//迭代器模式(Iterator)
//意图
//    提供一种方法顺序访问一个聚合对象中各个元素, 而又不需暴露该对象的内部表示。
//适用性
//    1.访问一个聚合对象的内容而无需暴露它的内部表示。
//    2.支持对聚合对象的多种遍历。
//    3.为遍历不同的聚合结构提供一个统一的接口(即, 支持多态迭代)。

namespace DesignPattern.IteratorRealWorld
{
    class IteratorRealWorld : AbstractPattern
    {
        public static void Run(TextBox tbInfo)
        {
            s_tbInfo = tbInfo;
            s_tbInfo.Text = "";

            // Build a collection 
            Collection collection = new Collection(); 
            collection[0] = new Item("Item 0"); 
            collection[1] = new Item("Item 1"); 
            collection[2] = new Item("Item 2"); 
            collection[3] = new Item("Item 3"); 
            collection[4] = new Item("Item 4"); 
            collection[5] = new Item("Item 5"); 
            collection[6] = new Item("Item 6"); 
            collection[7] = new Item("Item 7"); 
            collection[8] = new Item("Item 8"); 
            
            // Create iterator 
            Iterator  iterator = new Iterator (collection); 
            
            // Skip every other item 
            iterator.Step = 2;
            
            DesignPattern.FormMain.OutputInfo("Iterating over collection:"); 
            for (Item item = iterator.First(); !iterator.IsDone; item = iterator.Next()) 
            {
                DesignPattern.FormMain.OutputInfo(item.Name); 
            }
            
            // Wait for user 
            //Console.Read(); 
        }
    }
    class Item 
    {
        string name; 
        // Constructor 
        public Item(string name) 
        {
            this.name = name; 
        }
        // Property 
        public string Name 
        {
            get{ return name; } 
        }
    }
    
    // "Aggregate" 
    interface IAbstractCollection 
    {
        Iterator  CreateIterator(); 
    }
    
    // "ConcreteAggregate" 
    class Collection : IAbstractCollection 
    {
        private ArrayList items = new ArrayList(); 
        public Iterator  CreateIterator()
        { 
            return new Iterator (this); 
        }
        
        // Property 
        public int Count 
        {
            get{ return items.Count; } 
        }
        
        // Indexer 
        public object this[int index] 
        {
            get{ return items[index]; } 
            set{ items.Add(value); } 
        }
    }
    
    // "Iterator" 
    interface IAbstractIterator 
    {
        Item First(); 
        Item Next();
        bool IsDone{ get; } 
        Item CurrentItem{ get; } 
    }
    
    // "ConcreteIterator" 
    class Iterator  : IAbstractIterator 
    {
        private Collection collection; 
        private int current = 0; 
        private int step = 1; 
        
        // Constructor 
        public Iterator (Collection collection) 
        {
            this.collection = collection; 
        }
        public Item First() 
        {
            current = 0; 
            return collection[current] as Item; 
        }
        public Item Next() 
        {
            current += step; 
            if (!IsDone) 
                return collection[current] as Item; 
            else 
                return null; 
        }
        
        // Properties 
        public int Step 
        {
            get{ return step; } 
            set{ step = value; } 
        }
        
        public Item CurrentItem 
        {
            get { return collection[current] as Item; }
        } 
        public bool IsDone 
        {
            get { return current >= collection.Count ? true : false; }
        }
    }
}