设计模式：观察者模式（2）C++版

观察者模式：对象之间的一对多关系，当主题变化时，依赖它的对象都会收到通知并自动更新。

C++示例代码如下：

/** CONTENTS: DESIGN PATTERN, OBSERVER PATTERN*   AUTHOR: YAO H. WANG*     TIME: 2013-10-18 22:47:48*  EDITION: 1** ALL RIGHTS RESERVED!*/#include <list>#include <iostream>using namespace std;class DisplayElement{virtual void display() = 0;};//观察者class Observer{public:virtual void update(float temperature, float humility, float pressure) = 0;};//主题class Subject{public:virtual void registerObserver(Observer *ob) = 0;virtual void removeObserver(Observer *ob) = 0;virtual void notifyObservers() = 0;};class CurrentConditionsDisplay: public Observer, public DisplayElement{private:Subject *su;float temperature, humility;public:CurrentConditionsDisplay(Subject *su){this->su = su;su->registerObserver(this);}void update(float temperature, float humility, float pressure){this->temperature = temperature;this->humility = humility;display();}void display(){cout << "Current Conditions: " << temperature <<"F degree and  " << humility << "% humility" << endl;}};class WeatherData: public Subject{private:list<Observer*> lo;float temperature, humility, pressure;public:WeatherData(){//Java中此处需要生成ArrayList对象}void registerObserver(Observer *ob){lo.push_back(ob);}void removeObserver(Observer *ob){lo.remove(ob);}typedef list<Observer*>::const_iterator locit;void notifyObservers(){for(locit l=lo.begin(); l!=lo.end(); ++l)(*l)->update(temperature, humility, pressure);}void measurementsChanged(float temperature, float humility, float pressure){this->temperature = temperature;this->humility = humility;this->pressure = pressure;notifyObservers();}};//测试void main(){WeatherData *wd = new WeatherData();Observer *ob = new CurrentConditionsDisplay(wd);wd->measurementsChanged(80, 65, 30.4f);delete wd;delete ob;}