设计模式——观察者模式

/**-----------------------------------------------------------------------------
 * @file     main.cpp
 *
 * @author @.com.cn
 *
 * @date     2013-10-25
 *
 * @brief
 *
 * @version
 *
 *----------------------------------------------------------------------------*/
#include <iostream>
#include <list>
#include <algorithm>

using namespace std;

class subject;
/* 观察者抽象类 */
class observer
{
public:
    virtual void update(subject *sub) {};
};

/* 对象抽象类 */
/* 解析:
 * (1)3个函数都有默认实现， 不使用纯虚的，否则子类要重新实现
 * (2)list<observer*> m_observerList; list存放observer*类型，
 * (3)扩展:纯虚类不能作为变量类型
            class a{
                virtual void f() = 0;
            };
            a b;
 */
class subject
{
public:
    virtual void attach(observer* o);
    virtual void detach(observer* o);
    virtual void notify();
private:
    list<observer*> m_observerList;
};

void subject::attach(observer* o)
{
    m_observerList.push_back(o);
}

void subject::detach(observer* o)
{
    m_observerList.remove(o);
}

/* list遍历 */
void subject::notify()
{
    list<observer*>::iterator it;
    for ( it = m_observerList.begin();
          it != m_observerList.end();
          it++ )
    {
        (*it)->update(this);
    }
}



/* 对象 */
class newsStand : public subject
{
public:
    void setState(int state);
    int getState();

private:
    int m_state;
};

void newsStand::setState(int state)
{
    m_state = state;
    notify();
}

int newsStand::getState()
{
    return m_state;
}

/* 观察者 */
class student : public observer
{
public:
    void update(subject *sub)
    {
        cout << m_name << " get notice, state = " << ((newsStand*)sub)->getState() << endl;
    }

    student(string name)
    {
        m_name = name;
    }

    ~student()
    {
    }
private:
    string m_name;
};

int main(int argc, char **argv)
{
    newsStand s;
    student s1("lucy");
    student *s2 = new student("mike");
    s.attach(&s1);
    s.attach (s2);
    s.setState(2);

    return 0;
}

参考：http://sishuok.com/forum/blogPost/list/5279.html
研磨设计模式 之 观察者模式(Observer) 1——跟着cc学设计系列