设计模式 之 享元

享元模式（Flyweight）
          运用共享技术有效地支持大量细粒度的对象。


        还记得那年夏天一起在作文本上玩过的五子棋吗？五子棋是一种两人对弈的纯策略型棋类游戏，它起源于中国古代的传统黑白棋种之中的一个，不仅能增强思维能力，提高智力，并且富含哲理，有助于修身养性。
                                               

    假设我们要做一个五子棋游戏的程序，该怎么做呢？看看五子棋游戏中的棋子，就是“黑子”和“白子”两种类型，假设每次都创建一个新的对象实例，是不是太消耗系统内存了呢？以下就为大家解决这一问题

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;

namespace 享元模式
{
    //抽象棋子类
    public abstract class AbstractChessman
    {
        //棋子坐标
        protected int x;
        protected int y;

        //棋子类别（黑|白）
        protected string chess;
        public AbstractChessman (string chess)
        {
            this.chess = chess;
        }

        //点坐标设置
        public abstract void point(int x,int y);
        //显示棋子信息
        public void show()
        {
            Console.WriteLine(this.chess+ "("+this.x+","+this.y +")");
        }
    }

    //黑色棋子实现
    public class BlackChessman :AbstractChessman
    {
        public BlackChessman()
            : base("●")
        {
            Console.WriteLine("--BlackChessman Construction Exec!!!");
        }

        public override void point(int x,int y)
        {
            this.x = x;
            this.y = y;
            this.show();
        }
    }

    //白色棋子实现
    public class WhiteChessman :AbstractChessman
    {
        public WhiteChessman()
            : base("○")
        {
            Console.WriteLine("--WhiteChessman Construction Exec!!!");
        }

        public override void point(int x, int y)
        {
            this.x = x;
            this.y = y;
            this.show();
        }
    }

    //创建棋子工厂
    public class FiveChessmanFactory
    {
        //单例模式工厂
        private static FiveChessmanFactory fiveChessmanFactory = new FiveChessmanFactory();

        //缓存存放共享对象
        private Hashtable cache = new Hashtable();

        //私有化构造方法
        private FiveChessmanFactory()
        { }

        //获得单例工厂
        public static FiveChessmanFactory getInstance()
        {
            return fiveChessmanFactory;
        }
        
        public AbstractChessman getChessmanObject(string c)
        {
            //从缓存中获得棋子对象实例
            AbstractChessman abstractChessman = (AbstractChessman)this.cache[c];
            if (abstractChessman == null)
            {
                //缓存中没有棋子对象实例信息，则创建棋子对象实例，并放入缓存
                switch (c)
                {
                    case "B":
                        abstractChessman = new BlackChessman();
                        break;
                    case "W":
                        abstractChessman = new WhiteChessman();
                        break;
                    default:
                        break;

                }

                //为防止非法字符的进入，返回null
                if (abstractChessman !=null)
                {
                    cache.Add(c, abstractChessman);
                }
            }
            return abstractChessman;
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            //创建五子棋工厂
            FiveChessmanFactory fiveChessmanFactory = FiveChessmanFactory.getInstance();

            //随机数，用来生成棋子对象
            Random random = new Random();
            int radom = 0;
            AbstractChessman abstractChessman = null;

            for (int i = 0; i < 10; i++)
            {
                radom = random.Next(2);
                switch (radom)
                {
                    case 0:
                        abstractChessman = fiveChessmanFactory.getChessmanObject("B");
                        break;
                    case 1:
                        abstractChessman = fiveChessmanFactory.getChessmanObject("W");
                        break;
                }

                if (abstractChessman !=null)
                {
                    //设置棋子位置信息
                    abstractChessman.point(i, random.Next(15));
                }
            }
        }
    }
}