享元模式

【1】什么是享元模式？

享元模式：

【2】享元模式的代码示例：

代码示例1：

#include <iostream>
#include <string>
#include <map>
using namespace std;

class Flyweight
{
public:
    virtual void operation(int) = 0;
};

class ConcreteFlyweight : public Flyweight
{
    void operation(int extrinsicState)
    {
        cout << "具体FlyWeight: " << extrinsicState << endl;
    }
};

class UnsharedConcreteFlyweight : public Flyweight
{
    void operation(int extrinsicState)
    {
        cout << "不共享的具体FlyWeight: " << extrinsicState << endl;        
    }
};

class FlyweightFactory
{
private:
    map<string,Flyweight*> flyweights;
public:
    FlyweightFactory()
    {
        flyweights["X"] = new ConcreteFlyweight();
        flyweights["Y"] = new ConcreteFlyweight();
        flyweights["Z"] = new UnsharedConcreteFlyweight();
    }
    Flyweight *getFlyweight(string key)
    {
        return (Flyweight *)flyweights[key];
    }
};

int main()
{
    int state = 22;
    FlyweightFactory *f = new FlyweightFactory();
    
    Flyweight *fx = f->getFlyweight("X");
    fx->operation(--state);
    
    Flyweight *fy = f->getFlyweight("Y");
    fy->operation(--state);

    Flyweight *fz = f->getFlyweight("Z");
    fz->operation(--state);

    Flyweight *uf = new UnsharedConcreteFlyweight();
    uf->operation(--state);

    return 0;
}
//Result:
/*
具体FlyWeight: 21
具体FlyWeight: 20
不共享的具体FlyWeight: 19
不共享的具体FlyWeight: 18
*/

代码示例2：

#include <iostream>
#include <list>
#include <string>
#include <map>
using namespace std;

class WebSite
{
public:
    virtual void use() = 0;
}; 

class ConcreteWebSite : public WebSite
{
private:
    string name;
public:
    ConcreteWebSite(string name)
    {
        this->name = name;
    }
    void use()
    {
        cout << "网站分类: " << name << endl;
    }
};

class WebSiteFactory
{
private:
    map<string,WebSite*> wf;
public:
     
    WebSite *getWebSiteCategory(string key)
    {
        if (wf.find(key) == wf.end())
        {
            wf[key] = new ConcreteWebSite(key);
        }    
        return wf[key];
    }
     
    int getWebSiteCount()
    {
        return wf.size();
    }
};

int main()
{
    WebSiteFactory *wf = new WebSiteFactory();

    WebSite *fx = wf->getWebSiteCategory("good");
    fx->use();
    
     WebSite *fy = wf->getWebSiteCategory("产品展示");
    fy->use();

    WebSite *fz = wf->getWebSiteCategory("产品展示");
    fz->use();


    WebSite *f1 = wf->getWebSiteCategory("博客");
    f1->use();

    WebSite *f2 = wf->getWebSiteCategory("微博");
    f2->use();

    cout << wf->getWebSiteCount() << endl;
    return 0;
}
//Result:
/*
网站分类: good
网站分类: 产品展示
网站分类: 产品展示
网站分类: 博客
网站分类: 微博
4
*/

 

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