設(shè)計(jì)模式-享元模式

場(chǎng)景：象棋中每粒子都是紅方兩顆黑方兩顆。比如：車，棋盤中總共有4個(gè)，常規(guī)做法是有4個(gè)對(duì)象，通過(guò)享元1個(gè)對(duì)象搞定。
代碼如下:

//棋子的外部狀態(tài)
class Protertys
    {
        public string name { get; set; }
        public string position { get; set; }
        public string color { get; set; }

        public string capacity { get; set; }

        public Protertys(string _name,string _position, string _color, string _capacity)
        {
            name = _name;
            position = _position;
            color = _color;
            capacity = _capacity;
        }

    }
//棋子類
abstract class Chess
    {
        protected string name;//內(nèi)部對(duì)象
        public Chess(string _name)
        {
            name = _name;
        }
        public abstract void Run(Protertys protertys);
    }
    class ChineseChess : Chess
    {
        public ChineseChess(string _name) : base(_name)
        {
        }

        public override void Run(Protertys protertys)
        {
            Console.WriteLine("名字：{0}，位置：{1}，顏色：{2}，性能：{3}", name,protertys.position,protertys.color, protertys.capacity);
        }
    }    
        //享元工廠，核心
        class ChessFactory
    {
        private Hashtable hashTable = new Hashtable();
        public Chess GetChess(string key)
        {
            if (!hashTable.ContainsKey(key))
            {
                hashTable.Add(key,new ChineseChess(key));//不存在就創(chuàng)建
            }
            return (Chess)hashTable[key];
        }

        public int GetChessCount()
        {
            return hashTable.Count;
        }
    }
        //前端
        static void Main(string[] args)
        {

            Protertys protertys = new Protertys("車","左邊第一個(gè)","紅色","走直線");
            Protertys protertys1 = new Protertys("車", "右邊第一個(gè)", "紅色", "走直線");
            Protertys protertys2 = new Protertys("車", "左邊第一個(gè)", "黑色", "走直線");
            Protertys protertys3 = new Protertys("車", "右邊第一個(gè)", "黑色", "走直線");

            Protertys protertys4 = new Protertys("馬", "左邊第二個(gè)", "紅色", "走日字");
            Protertys protertys5 = new Protertys("馬", "右邊第二個(gè)", "紅色", "走日字");
            Protertys protertys6 = new Protertys("馬", "左邊第二個(gè)", "黑色", "走日字");
            Protertys protertys7 = new Protertys("馬", "右邊第二個(gè)", "黑色", "走日字");

            ChessFactory chessFactory = new ChessFactory();
            Chess Chess1= chessFactory.GetChess(protertys.name);
            Chess Chess2 = chessFactory.GetChess(protertys1.name);
            Chess Chess3 = chessFactory.GetChess(protertys2.name);
            Chess Chess4 = chessFactory.GetChess(protertys3.name);

            Chess Chess5 = chessFactory.GetChess(protertys4.name);
            Chess Chess6 = chessFactory.GetChess(protertys5.name);
            Chess Chess7 = chessFactory.GetChess(protertys6.name);
            Chess Chess8 = chessFactory.GetChess(protertys7.name);

            Chess1.Run(protertys);
            Chess2.Run(protertys1);
            Chess3.Run(protertys2);
            Chess4.Run(protertys3);
            Chess5.Run(protertys4);
            Chess6.Run(protertys5);
            Chess7.Run(protertys6);
            Chess8.Run(protertys7);

            int count = chessFactory.GetChessCount();
            Console.WriteLine("總共有{0}個(gè)對(duì)象",count);
            Console.ReadLine();
        }

總結(jié)：棋盤上的車馬總共是8個(gè)對(duì)象，然后最終只生成了2個(gè)對(duì)象，大大節(jié)約了內(nèi)存。
享元模式就是運(yùn)用共享技術(shù)，有效的支持大量細(xì)粒度對(duì)象（字面意思很貼切：共享元數(shù)據(jù)）。
方式：把對(duì)象的特性抽離出來(lái)當(dāng)外部狀態(tài)然后傳入對(duì)象。
優(yōu)點(diǎn)：避免大量的相似的類開銷，可減少對(duì)象的實(shí)例數(shù)量。
缺點(diǎn)：程序復(fù)雜化。

和簡(jiǎn)單工廠類似，和單例模式類似。
單例只有一個(gè)實(shí)例，而享元可以有多個(gè)實(shí)例。