观察者模式：股票提醒
当股票的价格上涨或下降5%时，会通知持有该股票的股民，当股民听到价格上涨的消息时会买股票，当价格下降时会大哭一场
c++源代码：
#include<iostream>
#include<list>
using namespace std;
class MyObserver {
public:
virtual void response(int rate) {};
};
class MySubject {
protected:
list<MyObserver*>observers;
public:
/*注册方法*/
void attach(MyObserver*observer) {
observers.push_back(observer);
};
/*注销方法*/
void detach(MyObserver* observer) {
observers.remove(observer);
}
/*抽象通知方法*/
virtual void change(int rate) = 0;
};
class Stock : public MySubject {
public:
void change(int rate) {
list<MyObserver*>::iterator iter = observers.begin();
for (; iter != observers.end(); iter++)
(*iter)->response(rate);
}
};
class Holders :public MyObserver {
public:
void response(int rate) {
if (rate >= 5) {
cout << "股票上涨，买买买" << endl;
}
else if (rate <= -5) {
cout << "股票下跌，大哭一场" << endl;
}
else {
cout << "股票比较稳定，还好还好" << endl;
}
}
};
int main() {
MySubject* subject = new Stock();
MyObserver*obs1 = new Holders();
subject->attach(obs1);
cout << "****股票上涨****" << endl;
subject->change(5);
cout << endl;
cout << "****股票下跌****" << endl;
subject->change(-5);
cout << endl;
cout << "****股票稳定****" << endl;
subject->change(4);
cout << endl;
}
实现截图：
