12.享元模式(Flyweight Pattern)

using System;

using System.Collections;



namespace ConsoleApplication5

{

    class Program

    {

        /// <summary>

        /// 在软件开发过程，如果我们需要重复使用某个对象的时候，

        /// 如果我们重复地使用new创建这个对象的话，这样我们在内存就需要多次地去申请内存空间了，

        /// 这样可能会出现内存使用越来越多的情况，这样的问题是非常严重，然而享元模式可以解决这个问题，

        /// 下面具体看看享元模式是如何去解决这个问题的。

        /// </summary>

        /// <param name="args"></param>

        static void Main(string[] args)

        {

            CharactorFactory factory = new CharactorFactory();



            // Charactor "A"

            CharactorA ca = (CharactorA)factory.GetCharactor("A");

            ca.SetPointSize(12);

            ca.Display();



            // Charactor "B"

            CharactorB cb = (CharactorB)factory.GetCharactor("B");

            cb.SetPointSize(10);

            cb.Display();



            // Charactor "C"

            CharactorC cc = (CharactorC)factory.GetCharactor("C");

            cc.SetPointSize(14);

            cc.Display();



        }

    }



    // 字符工厂(负责创建和管理享元对象)

    public class CharactorFactory

    {

        // Fields

        private Hashtable charactors = new Hashtable();



        // Constructor 

        public CharactorFactory()

        {

            charactors.Add("A", new CharactorA());

            charactors.Add("B", new CharactorB());

            charactors.Add("C", new CharactorC());

        }



        // Method

        public Charactor GetCharactor(string key)

        {

            Charactor charactor = charactors[key] as Charactor;



            if (charactor == null)

            {

                switch (key)

                {

                    case "A": charactor = new CharactorA(); break;

                    case "B": charactor = new CharactorB(); break;

                    case "C": charactor = new CharactorC(); break;

                    //

                }

                charactors.Add(key, charactor);

            }

            return charactor;

        }

    }



    /// <summary>

    /// 字符特殊类，提供具体享元类具有的方法

    /// </summary>

    public abstract class Charactor

    {

        //Fields

        protected char _symbol;

        protected int _width;

        protected int _height;

        protected int _ascent;

        protected int _descent;

        protected int _pointSize;



        //Method

        public abstract void SetPointSize(int size);

        public abstract void Display();

    }



    /// <summary>

    /// 字符A

    /// </summary>

    public class CharactorA : Charactor

    {

        // Constructor 

        public CharactorA()

        {

            this._symbol = 'A';

            this._height = 100;

            this._width = 120;

            this._ascent = 70;

            this._descent = 0;

            this._pointSize = 12;

        }



        //Method

        public override void SetPointSize(int size)

        {

            this._pointSize = size;

        }



        public override void Display()

        {

            Console.WriteLine(this._symbol +

              "pointsize:" + this._pointSize);

        }

    }



    /// <summary>

    /// 字符B

    /// </summary>

    public class CharactorB : Charactor

    {

        // Constructor 

        public CharactorB()

        {

            this._symbol = 'B';

            this._height = 100;

            this._width = 140;

            this._ascent = 72;

            this._descent = 0;

            this._pointSize = 10;

        }



        //Method

        public override void SetPointSize(int size)

        {

            this._pointSize = size;

        }



        public override void Display()

        {

            Console.WriteLine(this._symbol +

              "pointsize:" + this._pointSize);

        }

    }



    /// <summary>

    /// 字符C

    /// </summary>

    public class CharactorC : Charactor

    {

        // Constructor 

        public CharactorC()

        {

            this._symbol = 'C';

            this._height = 100;

            this._width = 160;

            this._ascent = 74;

            this._descent = 0;

            this._pointSize = 14;

        }



        //Method

        public override void SetPointSize(int size)

        {

            this._pointSize = size;

        }



        public override void Display()

        {

            Console.WriteLine(this._symbol +

              "pointsize:" + this._pointSize);

        }

    }



}