设计模式学习之----观察者模式

观察者模式

定义：定义对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并被自动更新。

大体实现：基类中维护观察者列表，声明接口及公共方法，观察者调用update刷新自己的状态。

#include <iostream>
#include <string>
#include <list>

using namespace std;
//秘书通知的发出者 

class Secretary;
//观察者
class PlayerObserver
{
public:
    PlayerObserver(Secretary *secretary)
    {
        m_secretary = secretary;
    }
    void update(string action)
    {
        cout << "action:" << action << endl;
    }

private:
    Secretary * m_secretary; //个人感觉可有可无
};

//主函数对这个类进行编程
class Secretary
{
public:
    void Notify(string Info)
    {
        for (list <PlayerObserver*>::iterator it = m_list.begin(); it != m_list.end(); it++)
        {
            (*it)->update(Info);
        }
    }

    void setPlayerObserver(PlayerObserver *obj)
    {
        m_list.push_back(obj);
    }

private:
    list <PlayerObserver*> m_list;
};


int main()
{
    PlayerObserver    *po1 = nullptr;
    PlayerObserver    *po2 = nullptr;
    Secretary        *sec = nullptr;

    sec = new Secretary;
    po1 = new PlayerObserver(sec);
    po2 = new PlayerObserver(sec);

    sec->setPlayerObserver(po1);
    sec->setPlayerObserver(po2);

    sec->Notify("boss is coming");
    sec->Notify("boss is going out");

    delete sec;
    delete po1;
    delete po2;

    return system("pause");
}