1 // 观察者模式.cpp : 定义控制台应用程序的入口点。 2 // 3  4 #include "stdafx.h" 5 #include<iostream> 6 #include <list> 7 #include<string> 8 using namespace std; 9 class Observer10 {11 public:12     Observer(){}13     virtual ~Observer(){}14     virtual void update(){}15 };16 //抽象主题17 class Subject18 {19 private:20     typedef list<Observer* >LIST;          //观察者链表 21     LIST observers;22 protected:23     string subjectstate;24 public:25     Subject(){}26     virtual ~Subject(){}27     void add_observer(Observer *observer)  //添加观察者28     {29         observers.push_back(observer);30     }31     void remove_observer(Observer *observer)//删除观察者32     {33         observers.remove(observer); 34     }35     virtual void  set_subjectstate(string )=0;//设置当前主题的状态36     virtual string get_subjectstate()=0;//观察当前主题的状态37     void notify()38     {39         LIST::iterator node = observers.begin();  40         for(; node != observers.end(); node++) 41         {42              (*node)->update(); 43         }44     }45 };46 47 class Concretesubject:public Subject48 {    49 public:50     Concretesubject (){}51     virtual~Concretesubject (){}52     virtual void  set_subjectstate(string s)53     {54         subjectstate=s;55     }56     virtual string get_subjectstate()57     {58         return subjectstate;59     }60 };61 62 class Concereteobserver:public Observer63 {64 private:65     Subject * subject;66 public:67     Concereteobserver(Subject *s)68     {69         subject=s;70     }71     ~Concereteobserver(){}72     void update()73     {74         string state=subject->get_subjectstate();75         if(state=="点名了")76         {77             cout<<"赶紧跑去上课"<<endl;78         }79         if(state=="正常上课")80         {81             cout<<"继续泡实验室"<<endl;82         }83     }84 };85 int _tmain(int argc, _TCHAR* argv[])86 {87     //创建一个具体的主题，上课老师是否点名88     Subject *dianming=new Concretesubject();89     //创造两个人 小尹和小胥90     Observer * xiaoyin=new Concereteobserver(dianming);91     Observer * xiaoxu=new Concereteobserver(dianming);92     //将小尹和小胥两个人注册为该主题的观察者93     dianming->add_observer(xiaoyin);94     dianming->add_observer(xiaoxu);95     //该主题发生变化的时候，自动通知他们，然后他们采取措施96     dianming->set_subjectstate("点名了");97     dianming->notify();98     return 0;99 }