观察者模式 observer

Observer是一种1对多的模式

Subject类用来通知 Observer类用来响应通知

 

Subject类内部有一个Observer类的指针链表 每当Subject类消息被触发时 遍历该链表来调用Observer类的响应

 

Obesrver模式的实现要点是,

第一一般subject类都是采用链表等容器来存放Observer对象,

第二抽取出Observer对象的一些公共的属性形成Observer基类,而Subject中保存的则是Observer类对象的指针,这样就使Subject和具体的Observer实现了解耦

 

具体实现

#ifndef _OBSERVER_#define _OBSERVER_#include <list>class Observer;class Subject{public:Subject();~Subject();void Notify();void Attach(Observer* pOb);void Detach(Observer* pOb);private:std::list<Observer*> m_list;};class Observer{public:Observer(){};~Observer(){};virtual void Update() = 0;};class ObserverCar : public Observer{public:ObserverCar(){};~ObserverCar(){};virtual void Update();};class ObserverBus : public Observer{public:ObserverBus(){};~ObserverBus(){};virtual void Update();};#endif

 

#include "stdafx.h"#include "Observer.h"Subject::Subject(){m_list.empty();}Subject::~Subject(){m_list.empty();}void Subject::Attach(Observer* pOb){m_list.push_back(pOb);}void Subject::Detach(Observer* pOb){std::list<Observer*>::iterator iter;for(iter = m_list.begin(); iter != m_list.end(); iter++){if((*iter) == pOb)m_list.erase(iter);}}void Subject::Notify(){if(m_list.empty())return;std::list<Observer*>::iterator iter;for(iter = m_list.begin(); iter != m_list.end(); iter++){(*iter)->Update();}}void ObserverCar::Update(){printf("Update car/n");}void ObserverBus::Update(){printf("Update bus/n");}int _tmain(int argc, _TCHAR* argv[]){Subject* pSub = new Subject();Observer* pCar = new ObserverCar();Observer* pBus = new ObserverBus();pSub->Attach(pCar);pSub->Attach(pBus);pSub->Notify();delete pSub;delete pCar;delete pBus;return 0;}