结构型模式篇-享元模式（Flyweight Pattern）-技术开发专区

结构型模式篇-享元模式（Flyweight Pattern）

作者：Terrylee 编辑：晓熊 2007-05-10 16:51

按照这样的实现思路，可以发现如果有多个客户端程序使用的话，会出现大量的重复性的逻辑，用重构的术语来说是出现了代码的坏味道，不利于代码的复用和维护；另外把这些状态和行为移到客户程序里面破坏了封装性的原则。再次转变我们的实现思路，可以确定的是这些状态仍然属于Charactor对象，所以它还是应该出现在Charactor类中，对于不同的状态可以采取在客户程序中通过参数化的方式传入。类结构图如下：

// "Charactor"
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();
}

// "CharactorA"
public class CharactorA : Charactor
{
    // Constructor 
    public CharactorA()
    {
        this._symbol = 'A';
        this._height = 100;
        this._width = 120;
        this._ascent = 70;
        this._descent = 0;
    }

    //Method
    public override void SetPointSize(int size)
    {
        this._pointSize = size;
    }

    public override void Display()
    {
        Console.WriteLine(this._symbol +
          "pointsize:" + this._pointSize);
    }
}

// "CharactorB"
public class CharactorB : Charactor
{
    // Constructor 
    public CharactorB()
    {
        this._symbol = 'B';
        this._height = 100;
        this._width = 140;
        this._ascent = 72;
        this._descent = 0;
    }

    //Method
    public override void SetPointSize(int size)
    {
        this._pointSize = size;
    }

    public override void Display()
    {
        Console.WriteLine(this._symbol +
          "pointsize:" + this._pointSize);
    }
}

// "CharactorC"
public class CharactorC : Charactor
{
    // Constructor 
    public CharactorC()
    {
        this._symbol = 'C';
        this._height = 100;
        this._width = 160;
        this._ascent = 74;
        this._descent = 0;
    }

    //Method
    public override void SetPointSize(int size)
    {
        this._pointSize = size;
    }

    public override void Display()
    {
        Console.WriteLine(this._symbol +
          "pointsize:" + this._pointSize);
    }
}

// "CharactorFactory"
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;
    }
}

public class Program
{
    public static void Main()
    {
        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");
        ca.SetPointSize(10);
        ca.Display();

        // Charactor "C"
        CharactorC cc = (CharactorC)factory.GetCharactor("C");
        ca.SetPointSize(14);
        ca.Display();
    }
}

第1页：概述第2页：创建一个实例第3页：引入CharactorFactory类第4页：小结

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