设计模式之享元模式

享元模式：运用共享技术有效地支持大量细粒度的对象

FlyweightFactory(工厂类)
负责产生和管理Flyweight的组件
内部通常使用容器类来存储共享的Flyweight组件
提供工厂方法产生对应的组件，当产生的是共享组件时，就加入到Flyweight管理容器内

Flyweight(组件接口)
定义组件的操作接口

ConcreteFlyweight(可以共享的组件)
实现Flyweight接口
产生的组件时可以共享的，并加入到Flyweight管理器中

UnsharedConcreteFlyweight(不可以共享的组件)
实现Flyweight接口，也可以选择不继承自Flyweight接口
可以定义为单独的组件，不包含任何共享资源
也可以讲一些共享组件定义为类的成员，成为内部状态；并另外定义其他不被共享的成员，作为外部状态使用

 class Program
    {
        static void Main(string[] args)
        {
            int extrinsicstate = 25;

            FlyweightFactory f = new FlyweightFactory();

            Flyweight fx = f.GetFlyweight("X");
            fx.Operation(--extrinsicstate);


            Flyweight fy = f.GetFlyweight("Y");
            fx.Operation(--extrinsicstate);

            Flyweight fz = f.GetFlyweight("Z");
            fx.Operation(--extrinsicstate);

            Flyweight uf = new UnsharedConcreteFlyweight();

            uf.Operation(--extrinsicstate);


            Console.ReadLine();
        }
    }
    abstract class Flyweight
    {
        public abstract void Operation(int extrinsicstate);

    }

    class ConcreteFlyweight : Flyweight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("具体Flyweight："+extrinsicstate);
        }
    }

    class UnsharedConcreteFlyweight : Flyweight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("不共享的具体Flyweight:"+extrinsicstate);
        }
    }

    class FlyweightFactory
    {

        private Hashtable flyweights = new Hashtable();
        public FlyweightFactory()
        {
            flyweights.Add("X", new ConcreteFlyweight());
            flyweights.Add("Y", new ConcreteFlyweight());
            flyweights.Add("Z", new ConcreteFlyweight());
        }
        public Flyweight GetFlyweight(string key)
        {
            return ((Flyweight)flyweights[key]);
        }
    }

享元模式的实例

 class Program
    {
        static void Main(string[] args)
        {
            WebSiteFactory f = new WebSiteFactory();

            WebSite fx = f.GetWebSiteCategory("网页");
            fx.Use();

            WebSite fy = f.GetWebSiteCategory("网页");
            fy.Use();

            WebSite fz = f.GetWebSiteCategory("网页");
            fz.Use();


            WebSite f1 = f.GetWebSiteCategory("博客");
            f1.Use();

            WebSite f2 = f.GetWebSiteCategory("博客");
            f2.Use();

            WebSite f3 = f.GetWebSiteCategory("博客");
            f3.Use();


            Console.WriteLine("网站分类总数为{0}",f.GetWebSiteCount());

            Console.ReadLine();
        }
    }

    abstract class WebSite
    {
        public abstract void Use();
    }

    class ConcreteWebSite : WebSite
    {
        private string name = "";

        public ConcreteWebSite(string name)
        {
            this.name = name;
        }
        public override void Use()
        {
            Console.WriteLine("网络分类："+name);
        }
    }

    class WebSiteFactory
    {
        private Hashtable flyweights = new Hashtable();

        //获得网站分类
        public WebSite GetWebSiteCategory(string key)
        {
            if (!flyweights.ContainsKey(key))
            {
                flyweights.Add(key, new ConcreteWebSite(key));
            }
            return ((WebSite)flyweights[key]);
        }

        //获得网站分离总数
        public int GetWebSiteCount()
        {
            return flyweights.Count;
        }
    }