设计模式5——观察者模式

观察这模式中，有一个观察者监听一个事件，当事件发生时，向所有被通知者发送相应的消息和命令。

例如，秘书作为观察者，监听老板的动作。当老板回来时，向看电影、睡觉的员工发送消息，让他们停止并开始工作。

Observation.h内容

#ifndef Observation_H_H
#define Observation_H_H

#include <iostream>
#include <vector>
using namespace std;

class Secretary;

class Boss
{
public:
    Boss();
    void comeBack();
    void setSecretary(Secretary *secretary0);
private:
    Secretary *secretary;
};

class Staff
{
public:
    virtual void getSingal() = 0;
    virtual ~Staff() {}
};

class StaffMovie : public Staff
{
public:
    virtual void getSingal() { cout << "Boss is coming, Stop watching movie!" << endl; }
};

class StaffSleep : public Staff
{
public:
    virtual void getSingal() { cout << "Boss is coming, Stop sleeping!" << endl; }
};

class Secretary
{
public:
    Secretary() : boss(NULL) {}
    void sendSingal(){
        for(size_t i=0; i<vecStaff.size(); ++i){
            vecStaff[i]->getSingal();
        }
    }

    void addStaff(Staff *staff) { vecStaff.push_back(staff); }
    void setBoss(Boss *boss0) { boss = boss0; }
private:
    Boss *boss;
    vector<Staff*> vecStaff;
};


Boss::Boss() : secretary(NULL) {}
void Boss::comeBack() { secretary->sendSingal(); }
void Boss::setSecretary(Secretary *secretary0) { secretary = secretary0; }

void ObservationTest()
{
    Boss *boss = new Boss();
    Staff *staff1 = new StaffMovie();
    Staff *staff2 = new StaffSleep();
    Secretary *secretary = new Secretary();
    secretary->addStaff(staff1);
    secretary->addStaff(staff2);
    secretary->setBoss(boss);
    boss->setSecretary(secretary);

    boss->comeBack();
}

#endif

运行结果：