第一：单纯享元模式。
1： 单纯享元模式结构图：
2：单纯享元模式构成说明：
1>:抽象享元(Flyweight)角色：此角色是所有的具体享元类的超类，为这些类规定出需要实现的公共接口。那些需要外蕴状态(External State)的操作可以通过调用商业方法以参数形式传入。
/// <summary>
/// "Flyweight"
/// </summary>
abstract class Flyweight
{
// Methods
/// <summary>
/// 抽象享元对象的商业方法
/// </summary>
/// <param name="extrinsicstate">外蕴状态</param>
abstract public void Operation(int extrinsicstate);
}
/// "Flyweight"
/// </summary>
abstract class Flyweight
{
// Methods
/// <summary>
/// 抽象享元对象的商业方法
/// </summary>
/// <param name="extrinsicstate">外蕴状态</param>
abstract public void Operation(int extrinsicstate);
}
2>:具体享元(ConcreteFlyweight)角色：实现抽象享元角色所规定的接口。如果有内蕴状态的话，必须负责为内蕴状态提供存储空间。享元对象的内蕴状态必须与对象所处的周围环境无关，从而使得享元对象可以在系统内共享的。
/// <summary>
/// "ConcreteFlyweight"
/// </summary>
class ConcreteFlyweight : Flyweight
{
private string intrinsicstate = "A";
// Methods
override public void Operation(int extrinsicstate)
{
Console.WriteLine("ConcreteFlyweight: intrinsicstate {0}, extrinsicstate {1}",
intrinsicstate, extrinsicstate);
}
}
/// "ConcreteFlyweight"
/// </summary>
class ConcreteFlyweight : Flyweight
{
private string intrinsicstate = "A";
// Methods
override public void Operation(int extrinsicstate)
{
Console.WriteLine("ConcreteFlyweight: intrinsicstate {0}, extrinsicstate {1}",
intrinsicstate, extrinsicstate);
}
}
3>:享元工厂(FlyweightFactory)角色：本角色负责创建和管理享元角色。本角色必须保证享元对象可以被系统适当地共享。当一个客户端对象调用一个享元对象的时候，享元工厂角色会检查系统中是否已经有一个复合要求的享元对象。如果已经有了，享元工厂角色就应当提供这个已有的享元对象；如果系统中没有一个适当的享元对象的话，享元工厂角色就应当创建一个合适的享元对象。
注意：客户端不可以直接实例化享元类,必须通过享元工厂类来创建,因为享元工厂类在系统中只能有一个,所以可以结合单例模式来改善。当客户端需要单纯享元对象时，需要调用享元工厂的Singleton()方法，此时工厂会取得所有的单纯享元对象，然后传入所需的单纯享元对象的内蕴状态，工厂方法负责产生所需要的享元对象。
/// <summary>
/// "FlyweightFactory"
/// </summary>
class FlyweightFactory
{
// Fields
private Dictionary<string, Flyweight> flyweights = new Dictionary<string, Flyweight>();
private static readonly FlyweightFactory instance = new FlyweightFactory();
/// <summary>
/// Constructors
/// </summary>
private FlyweightFactory()
{
}
// Methods
/// <summary>
/// 从享元工厂中生产出一个具体的享元对象
/// </summary>
/// <param name="key">内蕴状态</param>
/// <returns></returns>
public Flyweight GetFlyweight(string key)
{
return ((Flyweight)flyweights[key]);
}
/// <summary>
/// 享元工厂单例方法
/// </summary>
/// <returns></returns>
public static FlyweightFactory Singleton()
{
return FlyweightFactory.instance;
}
/// <summary>
/// 向享元工厂对象增加一个享元对象
/// </summary>
/// <param name="sKey">内蕴状态</param>
/// <param name="_Flyweight">具体享元对象</param>
public void AddFlyweight(string sKey, Flyweight _Flyweight)
{
flyweights.Add(sKey , _Flyweight);
}
public Flyweight factory(string sKey)
{
if (flyweights.ContainsKey(sKey))
{
return this.GetFlyweight(sKey);
}
else
{
this.AddFlyweight(sKey, new ConcreteFlyweight());
return this.GetFlyweight(sKey);
}
}
}
/// "FlyweightFactory"
/// </summary>
class FlyweightFactory
{
// Fields
private Dictionary<string, Flyweight> flyweights = new Dictionary<string, Flyweight>();
private static readonly FlyweightFactory instance = new FlyweightFactory();
/// <summary>
/// Constructors
/// </summary>
private FlyweightFactory()
{
}
// Methods
/// <summary>
/// 从享元工厂中生产出一个具体的享元对象
/// </summary>
/// <param name="key">内蕴状态</param>
/// <returns></returns>
public Flyweight GetFlyweight(string key)
{
return ((Flyweight)flyweights[key]);
}
/// <summary>
/// 享元工厂单例方法
/// </summary>
/// <returns></returns>
public static FlyweightFactory Singleton()
{
return FlyweightFactory.instance;
}
/// <summary>
/// 向享元工厂对象增加一个享元对象
/// </summary>
/// <param name="sKey">内蕴状态</param>
/// <param name="_Flyweight">具体享元对象</param>
public void AddFlyweight(string sKey, Flyweight _Flyweight)
{
flyweights.Add(sKey , _Flyweight);
}
public Flyweight factory(string sKey)
{
if (flyweights.ContainsKey(sKey))
{
return this.GetFlyweight(sKey);
}
else
{
this.AddFlyweight(sKey, new ConcreteFlyweight());
return this.GetFlyweight(sKey);
}
}
}
4>:客户端(Client)角色：需要维护一个对所有享元对象的引用;需要自行存储所有享元对象外蕴状态。
// 初始化外蕴状态值
int extrinsicstate = 22;
//享元工厂对象使用单例
FlyweightFactory f = FlyweightFactory.Singleton () ;
//调用过程
//向享元工厂对象请求一个内蕴状态为"X"的单纯享元对象
Flyweight fx = f.factory("X");
//调用X的商业方法,X的外蕴状态值为21
fx.Operation(--extrinsicstate);
Flyweight fy = f.factory("Y");
fy.Operation(--extrinsicstate);
Flyweight fz = f.factory("Z");
fz.Operation(--extrinsicstate);
int extrinsicstate = 22;
//享元工厂对象使用单例
FlyweightFactory f = FlyweightFactory.Singleton () ;
//调用过程
//向享元工厂对象请求一个内蕴状态为"X"的单纯享元对象
Flyweight fx = f.factory("X");
//调用X的商业方法,X的外蕴状态值为21
fx.Operation(--extrinsicstate);
Flyweight fy = f.factory("Y");
fy.Operation(--extrinsicstate);
Flyweight fz = f.factory("Z");
fz.Operation(--extrinsicstate);
