[设计模式]<5>. C++与享元模式(flyweight pattern)

默默的EEer

原文地址：

http://www.cnblogs.com/hebaichuanyeah/p/5616427.html

享元模式指“运用共享技术有效地支持大量细粒度的对象”。

java中的string对象就是利用的享元模式，不同的string对象相同的字符串，则实质指向的字符串地址是一样的。（事实上java里面的事件机制就是所谓观察者模式）

一个极其简单的例子

#include <iostream>
#include <map>

using namespace std;

class Flyweight
{
protected:
    string name;
public:
    Flyweight(){}
    virtual ~Flyweight(){}
    virtual void Operation()
    {

    }
};

class someObject: public Flyweight
{

public:
    someObject(string str)
    {
        cout<<"创建一个"<<name<<"对象"<<endl;
        name = str;
    }
    virtual void Operation()
    {
        cout<<name<<"对象操作"<<endl;
    }

};
class FlyweightFactory
{
    //
private:
    map<string,Flyweight *>  flyweightMap;
    Flyweight * ret;
public:
    Flyweight * getFlyweight(string name)
    {
        if(flyweightMap.count(name))
            ret =flyweightMap[name];
        else
        {
            ret = new someObject(name);
            flyweightMap.insert(pair<string,Flyweight *>(name, ret));
        }
        return ret;
    }
};

main()
{
    FlyweightFactory flyweightFactory;
    Flyweight * test = flyweightFactory.getFlyweight("test");
}