设计模式-观察者模式

适用模式:多个观察者同时监听一个主题对象.

// subject.h
#ifndef SUBJECT_H
#define SUBJECT_H

#include <vector>
#include "observer.h"

class Observer;

class Subject
{
public:
    Subject();
    virtual void Attach(Observer * observer) = 0;
    virtual void Nofity() = 0;
public:
    int m_message;
    std::vector<Observer*> m_observers;
};

#endif // SUBJECT_H

// subject.cpp
#include "subject.h"

Subject::Subject()
{
    m_message = 0;
}

// concretesubject.h
#ifndef CONCRETESUBJECT_H
#define CONCRETESUBJECT_H

#include "subject.h"

class ConcreteSubject : public Subject
{
public:
    ConcreteSubject();
    virtual void Attach(Observer * observer);
    virtual void Nofity();
};

#endif // CONCRETESUBJECT_H

// concretesubject.cpp
#include "concretesubject.h"

ConcreteSubject::ConcreteSubject()
{}

void ConcreteSubject::Attach(Observer *observer)
{
    m_observers.push_back(observer);
}

void ConcreteSubject::Nofity()
{
    std::vector<Observer*>::iterator it = m_observers.begin();
    while( it != m_observers.end())
    {
        (*it)->Update();
        it++;
    }
}

// observer.h
#ifndef OBSERVER_H
#define OBSERVER_H

#include "subject.h"

class Subject;

class Observer
{
public:
    Observer(int state, Subject *sub);
    virtual void Update() = 0;
public:
    int m_state;
    Subject *m_sub;
};

#endif // OBSERVER_H

// observer.cpp
#ifndef CONCRETESUBJECT_H
#define CONCRETESUBJECT_H

#include "subject.h"

class ConcreteSubject : public Subject
{
public:
    ConcreteSubject();
    virtual void Attach(Observer * observer);
    virtual void Nofity();
};

#endif // CONCRETESUBJECT_H

// concreteobserver.h
#ifndef CONCRETEOBSERVER_H
#define CONCRETEOBSERVER_H

#include "observer.h"

class ConcreteObserver : public Observer
{
public:
    ConcreteObserver(int state, Subject *sub);
    virtual void Update();
};

#endif // CONCRETEOBSERVER_H

// concreteobserver.cpp
#include "concreteobserver.h"
#include <iostream>

ConcreteObserver::ConcreteObserver(int state, Subject *sub) : Observer(state, sub)
{}

void ConcreteObserver::Update()
{
    m_state = m_sub->m_message + 10000;
    std::cout << m_sub->m_message << ":::" << m_state << std::endl;
}

客户端:

// main.cpp
#include <iostream>
#include "subject.h"
#include "observer.h"
#include "concreteobserver.h"
#include "concretesubject.h"

using namespace std;

int main(int argc, char *argv[])
{
    Subject *sub = new ConcreteSubject();
    Observer *observer = new ConcreteObserver(0, sub);

    sub->Attach(observer);

    sub->m_message = 2;

    sub->Nofity();

    return 0;
}