厦门做网站多少,百度竞价是什么意思?,成都倒闭的网站建设公司名单,南宁手机建站公司介绍 享元模式运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象#xff0c;而这些对象都很相似#xff0c;状态变化很小#xff0c;可以实现对象的多次复用。由于享元模式要求能够共享的对象必须是细粒度对象#xff0c;因此它又称为轻量级模式#xff…介绍 享元模式运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象而这些对象都很相似状态变化很小可以实现对象的多次复用。由于享元模式要求能够共享的对象必须是细粒度对象因此它又称为轻量级模式是一种对象结构型模式。 实现
myclass.h
//
// Created by yuwp on 2024/1/12.
//#ifndef DESIGNPATTERNS_MYCLASS_H
#define DESIGNPATTERNS_MYCLASS_H#include iostream
#include unordered_mapclass Flyweight { // 享元抽象类
public:Flyweight(const std::string in);virtual void operation(const std::string out) 0;const std::string getMIn() const;private:std::string m_in;
};class ConcreteFlyweight : public Flyweight { // 具体享元类
public:ConcreteFlyweight(const std::string in);void operation(const std::string out) override;
};class FlyweightFactory { // 配合工厂模式使用享元工厂类
public:~FlyweightFactory();Flyweight *getFlyweight(const std::string key);
private:std::unordered_mapstd::string, Flyweight * m_flyweights;
};#endif //DESIGNPATTERNS_MYCLASS_Hmyclass.cpp
//
// Created by yuwp on 2024/1/12.
//#include myclass.hFlyweight::Flyweight(const std::string in) {m_in in;
}const std::string Flyweight::getMIn() const {return m_in;
}ConcreteFlyweight::ConcreteFlyweight(const std::string in) : Flyweight(in) {}void ConcreteFlyweight::operation(const std::string out) {std::cout 内部状态: getMIn() , 外部状态: out std::endl;
}FlyweightFactory::~FlyweightFactory() {for (auto it : m_flyweights) {if (it.second) {delete it.second;}}
}Flyweight* FlyweightFactory::getFlyweight(const std::string key) {auto it m_flyweights.find(key);if (it ! m_flyweights.end()) {return it-second;} else {Flyweight *flyweight new ConcreteFlyweight(key);m_flyweights.insert(std::make_pair(key, flyweight));return flyweight;}
}
main.cpp
#include iostream
#include mutex
#include myclass.hint main() {FlyweightFactory *factory new FlyweightFactory();auto fly1 factory-getFlyweight(a);auto fly2 factory-getFlyweight(b);auto fly3 factory-getFlyweight(a);fly1-operation(1);fly2-operation(2);fly3-operation(3);delete factory;return 0;
}
总结
优点 1. 可以极大减少内存中对象的数量使得相同或相似对象在内存中只保存一份从而可以节约系统资源提高系统性能。 2. 享元模式的外部状态相对独立而且不会影响其内部状态从而使得享元对象可以在不同的环境中被共享。
缺点 1. 享元模式需要分离出内部状态和外部状态从而使得系统变得复杂这使得程序的逻辑复杂化。 2. 为了使对象可以共享享元模式需要将享元对象的部分状态外部化而读取外部状态将使得运行时间变长。
适用场景 1. 一个系统有大量相同或者相似的对象造成内存的大量耗费。 2. 对象的大部分状态都可以外部化可以将这些外部状态传入对象中。 3. 在使用享元模式时需要维护一个存储享元对象的享元池而这需要耗费一定的系统资源。因此在需要多次重复使用同一享元对象时才值得使用享元模式。 练习
myclass.h
//
// Created by yuwp on 2024/1/12.
//#ifndef DESIGNPATTERNS_MYCLASS_H
#define DESIGNPATTERNS_MYCLASS_H#include iostream
#include unordered_mapclass Flyweight { // 享元抽象类
public:Flyweight(const std::string in);virtual void display(const std::string out) 0;const std::string getMIn() const;private:std::string m_in;
};class PictureFlyweight : public Flyweight { // 具体享元类
public:PictureFlyweight(const std::string in);void display(const std::string out) override;
};class AnimationFlyweight : public Flyweight { // 具体享元类
public:AnimationFlyweight(const std::string in);void display(const std::string out) override;
};class VideoFlyweight : public Flyweight { // 具体享元类
public:VideoFlyweight(const std::string in);void display(const std::string out) override;
};class FlyweightFactory { // 配合工厂模式使用享元工厂类
public:~FlyweightFactory();Flyweight *getFlyweight(const std::string key);static FlyweightFactory *getInstance();
private:FlyweightFactory();std::unordered_mapstd::string, Flyweight * m_flyweights;
};#endif //DESIGNPATTERNS_MYCLASS_Hmyclass.cpp
//
// Created by yuwp on 2024/1/12.
//#include myclass.hFlyweight::Flyweight(const std::string in) {m_in in;
}const std::string Flyweight::getMIn() const {return m_in;
}PictureFlyweight::PictureFlyweight(const std::string in) : Flyweight(in) {}void PictureFlyweight::display(const std::string out) {std::cout out , getMIn() std::endl;
}AnimationFlyweight::AnimationFlyweight(const std::string in) : Flyweight(in) {}void AnimationFlyweight::display(const std::string out) {std::cout out , getMIn() std::endl;
}VideoFlyweight::VideoFlyweight(const std::string in) : Flyweight(in) {}void VideoFlyweight::display(const std::string out) {std::cout out , getMIn() std::endl;
}FlyweightFactory::FlyweightFactory() {}FlyweightFactory* FlyweightFactory::getInstance() {static FlyweightFactory *factory new FlyweightFactory();return factory;
}FlyweightFactory::~FlyweightFactory() {for (auto it : m_flyweights) {if (it.second) {delete it.second;}}
}Flyweight* FlyweightFactory::getFlyweight(const std::string key) {auto it m_flyweights.find(key);if (it ! m_flyweights.end()) {return it-second;} else {Flyweight *flyweight nullptr;if (key 图片) {flyweight new PictureFlyweight(key);} else if (key 动画) {flyweight new AnimationFlyweight(key);} else if (key 视频) {flyweight new VideoFlyweight(key);}m_flyweights.insert(std::make_pair(key, flyweight));return flyweight;}
}
main.cpp
#include iostream
#include mutex
#include myclass.hint main() {FlyweightFactory *factory FlyweightFactory::getInstance();factory-getFlyweight(图片)-display(1);factory-getFlyweight(动画)-display(2);factory-getFlyweight(视频)-display(3);factory-getFlyweight(图片)-display(4);return 0;
}
