C++设计模式之享元模式(FlyWeight)

逃离我推掉我的手 2022-08-02 09:50 178阅读 0赞

FlyWeight享元模式,其实就是为C++在构造大量对象的时候进行减肥,以减少内存的使用,
    其特征是工厂类里包含了缓冲区模式,以下两种实现的区别就是第一种汽车有将其m_Brand的品牌提取到一个FlyWeight,将公共数据成员共享!
    #include "StdAfx.h"
    #include <SSTREAM>
    #include<iostream>
    #include<fstream>
    #include<malloc.h>
    #include <windows.h>
    #include <list>
    #include <map>
    using namespace std;
    class CarBody
    {//汽车
    public:
        CarBody(string Wheel,string Light,string Engine):
          m_Wheel(Wheel),m_Light(Light),m_Engine(Engine)
        {
     
        }
    protected:
    private:
        string m_Wheel;
        string m_Light;
        string m_Engine;
    };
     
    class FlyWeightCar
    {//享元汽车,将品牌的数据成员集合在一起
    public:
        FlyWeightCar(string Brand,CarBody* pCar):
          m_Car(pCar),m_Brand(Brand)
          {
     
          }
    protected:
    private:
        string m_Brand;
        CarBody* m_Car;
    };
     
    class FlyWeightFactory
    {//享元工厂
    public:
        FlyWeightCar* GetCar(string Brand,string Wheel,string Light,string Engine)
        {//享元模式的缓冲区
            if (m_FlyCars[Brand]!=NULL)
            {
                return m_FlyCars[Brand];
            }else{
                CarBody* pNew=new CarBody(Wheel,Light,Engine);
                FlyWeightCar* pNewFlyWeightCar=new FlyWeightCar(Brand,pNew);
                m_FlyCars[Brand]=pNewFlyWeightCar;
            }
        }
    protected:
    private:
        map<string ,FlyWeightCar*> m_FlyCars;//缓冲区
    };
    int main(void) 
    { 
        FlyWeightFactory pFactory;
        for (int i=0;i<2000;i++)
        {
            pFactory.GetCar("BMW","轮子","灯光","引擎");
        }
        return 0; 
    }
    第二种:
    #include "StdAfx.h"
    #include <SSTREAM>
    #include<iostream>
    #include<fstream>
    #include<malloc.h>
    #include <windows.h>
    #include <list>
    #include <map>
    using namespace std;
    class FlyWeight
    {//基类
    public:
        virtual void Operation()=0;
    protected:
    private:
    };
    class ConcreteFlyWeight:public FlyWeight
    {//继承与Flyweight
    public:
        string m_Key;
        virtual void Operation()
        {
            printf("%s",m_Key.c_str());
        }
    protected:
    private:
    };
    class FlyWeightFactory
    {
    public:
        map<string,ConcreteFlyWeight*> m_FlyWeightPool;//缓冲区
        ConcreteFlyWeight* GetConcreteFlyweight(string key)
        {
            if (NULL==m_FlyWeightPool[key])
            {
                ConcreteFlyWeight* pFlyWeight=new ConcreteFlyWeight();
                pFlyWeight->m_Key=key;
                m_FlyWeightPool[key]=pFlyWeight;
            }
            return m_FlyWeightPool[key];
        }
    protected:
    private:
    };
    int main(void) 
    { 
        FlyWeightFactory pFactory;
        FlyWeight* p1=pFactory.GetConcreteFlyweight("www.qq.com");
        FlyWeight* p2=pFactory.GetConcreteFlyweight("www.baidu.com");
        FlyWeight* p3=pFactory.GetConcreteFlyweight("www.qq.com");
        FlyWeight* p4=pFactory.GetConcreteFlyweight("www.baidu.com");
        p1->Operation();
        p2->Operation();
        p3->Operation();
        p4->Operation();
        return 0; 
    }