C++设计模式浅识观察者模式
程序员文章站
2022-04-20 10:52:05
...
观察者模式(Observer):定义了一种一对多的依赖关系,让多个观察者对象同时监听某一个主体对象。这个主题对象在状态发生变化时,会通知所有观察者对象,使它们能够自动更新自己。
模式实现:
模式实现:
[code]//观察者抽象基类 class Observer{ public: virtual void Update(int) = 0; }; //主题、目标 class Subject{ public: virtual void Attach(Observer *) = 0; //重视 virtual void Detach(Observer *) = 0; //脱离 virtual void Notify() = 0; //通知 }; class ConcreateObserver: public Observer{ private: Subject *m_pSubject; //1.具体观察者,维护一个指向ConcreteSubject对象的引用2.存储有关状态,这些状态应与目标的状态保持一致 public: //3.实现Observer的更新接口以使自身状态与目标的状态保持一致 ConcreateObserver(Subject *pSubject): m_pSubject(pSubject){} void Update(int value){ std::cout << "ConcreateObserver get the update. New State: " << value << std::endl; } }; class ConcreateObserver2: public Observer{ private: Subject *m_pSubject; public: ConcreateObserver2(Subject *pSubject):m_pSubject(pSubject){} void Update(int value){ std::cout << "ConcreateObserver2 get the update. New State: " << value << std::endl; } }; //1.将有关状态存入各ConcreateObserver对象 //2.当它的状态发生改变时,向它的各个观察者发出通知 class ConcreateSubject: public Subject{ private: std::list<Observer *> m_ObserverList; int m_iState; public: void Attach(Observer *pObserver); void Detach(Observer *pObserver); void Notify(); void setState(int state){ m_iState = state; } }; void ConcreateSubject::Attach(Observer *pObserver){ m_ObserverList.push_back(pObserver); } void ConcreateSubject::Detach(Observer *pObserver){ m_ObserverList.remove(pObserver); } void ConcreateSubject::Notify(){ std::list<Observer *>::iterator it = m_ObserverList.begin(); while(it != m_ObserverList.end()){ (*it)->Update(m_iState); ++it; } }
客户端:
[code]int main(){ //Create Subject ConcreateSubject *pSubject = new ConcreateSubject(); //Create Observer Observer *pObserver = new ConcreateObserver(pSubject); Observer *pObserver2 = new ConcreateObserver2(pSubject); //Change the state pSubject->setState(2); //Register the observer pSubject->Attach(pObserver); pSubject->Attach(pObserver2); pSubject->Notify(); //Output: ConcreateObserver get the update. New State: 2 //ConcreateObserver2 get the update. New State: 2 //Unregister the observer pSubject->Detach(pObserver); pSubject->setState(3); pSubject->Notify(); //Output: ConcreateObserver2 get the update. New State: 3 delete pObserver; delete pObserver2; delete pSubject; }
以上就是C++设计模式浅识观察者模式的内容,更多相关内容请关注PHP中文网(www.php.cn)!
上一篇: php动态地创建属性和方法实例代码详解
下一篇: ps破解补丁怎么用