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);
        }
    }

}