設計模式-享元模式

場景：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，常規做法是有4個對象，通過享元1個對象搞定。
代碼如下:

//棋子的外部狀態
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;//內部對象
        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","紅色","走直線");
            Protertys protertys1 = new Protertys("車", "右邊第一個", "紅色", "走直線");
            Protertys protertys2 = new Protertys("車", "左邊第一個", "黑色", "走直線");
            Protertys protertys3 = new Protertys("車", "右邊第一個", "黑色", "走直線");

            Protertys protertys4 = new Protertys("馬", "左邊第二個", "紅色", "走日字");
            Protertys protertys5 = new Protertys("馬", "右邊第二個", "紅色", "走日字");
            Protertys protertys6 = new Protertys("馬", "左邊第二個", "黑色", "走日字");
            Protertys protertys7 = new Protertys("馬", "右邊第二個", "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}個對象",count);
            Console.ReadLine();
        }

總結：棋盤上的車馬總共是8個對象，然后最終只生成了2個對象，大大節約了內存。
享元模式就是運用共享技術，有效的支持大量細粒度對象（字面意思很貼切：共享元數據）。
方式：把對象的特性抽離出來當外部狀態然后傳入對象。
優點：避免大量的相似的類開銷，可減少對象的實例數量。
缺點：程序復雜化。

和簡單工廠類似，和單例模式類似。
單例只有一個實例，而享元可以有多個實例。