C++实现观察者模式
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/*观察者模式：定义一种一对多的依赖，让多个观察者对象同时监听某一个主题对象，这个主题对象发生变化时，会通知所有观察者对象，使得他们能够自动更新自己*/#include <iostream>#include <vector>#include <string>#include <algorithm>using namespace std;class Observer{public:virtual void Update() {}};class Subject{vector<Observer*> observers;public:virtual void Notify(){vector<Observer*>::iterator iter = observers.begin();for(; iter != observers.end(); iter++){(*iter)->Update();}}void AddObserver(Observer *observer){observers.push_back(observer);}void DeleteObserver(Observer *observer){vector<Observer*>::iterator iter = observers.end();while(iter != observers.end()){if(*iter == observer){observers.erase(iter);}}}};class ConcreteSubject:public Subject{private:string subjectstate;public:ConcreteSubject(string state){subjectstate = state;}string State(){return subjectstate;}};class ConcreteObserver:public Observer{ConcreteSubject *subject;string name;public:ConcreteObserver(ConcreteSubject *subject,string name){this->subject = subject;this->name = name;}void Update(){cout<<"Observer "<<name<<" observer subject state is "<< this->subject->State()<<endl;}};int main(){ConcreteSubject *subject = new ConcreteSubject("unhappy");ConcreteObserver *observer1 = new ConcreteObserver(subject, "observer1");ConcreteObserver *observer2 = new ConcreteObserver(subject, "observer2");ConcreteObserver *observer3 = new ConcreteObserver(subject, "observer3");subject->AddObserver(observer1);subject->AddObserver(observer2);subject->AddObserver(observer3);subject->Notify();delete subject;delete observer1;delete observer2;delete observer3;system("pause");return 0;}
