观察者模式C++

一、今日学习内容

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++:

#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，购买股票" << endl;
        }
        else if (rate <= -5) {
            cout << "股票下跌，大哭一场" << endl;
        }
        else {
            cout << "股票还比较稳定哦~" << 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;
}

截图：