c++ 观察者模式(observer)

观察者模式: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。它还有两个别名,依赖 (Dependents),发布-订阅(Publish-Subsrcibe)。可以举个博客订阅的例子,当博主发表新文章的时候,即博主状态发生了改 变,那些订阅的读者就会收到通知,然后进行相应的动作,比如去看文章,或者收藏起来。博主与读者之间存在种一对多的依赖关系。下面给出相应的UML图设 计。

以博客和博客的粉丝(observer)为例

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

using namespace std;

class Observer
{
public:
    Observer() {}
    virtual ~Observer() {}
    virtual void Update() {}

};

class Blog
{
public:
    Blog(){}
    virtual ~Blog() {}
    void Attach(Observer *observer)
    {
        m_observers.push_back(observer);
    }
    void Remove(Observer* observer)
    {
        m_observers.remove(observer);
    }
    void Notify()
    {
        list<Observer*>::iterator iter = m_observers.begin();
        for(;iter != m_observers.end(); iter++)
            (*iter)->Update();
    }
    virtual void SetStatus(string s)
    {
        m_status = s;
    }
    virtual std::string GetStatus()
    {
        return m_status;
    }
private:
    list<Observer* > m_observers;
protected:
    std::string m_status;
};

class BlogBKY : public Blog
{
public:
    BlogBKY(string name):m_name(name) {}
    ~BlogBKY() {}
    void SetStatus(string s)
    {
        m_status = s ;
    }
    string GetStatus()
    {
        return m_status;
    }
private:
    string m_name;
};

class ObserverBlog : public Observer
{
public:
    ObserverBlog(string name,Blog *blog):m_name(name),m_blog(blog)
    {
    
    }
    ~ObserverBlog() {}
    void Update()
    {
        std::string status = m_blog->GetStatus();
        cout << m_name  <<"-------" << status <<endl;
    }
private:
    std::string m_name;
    Blog *m_blog;
};

接口的使用:

#include "observer.h"
int main()
{
    Blog *blog = new BlogBKY("onlycxue");
    Observer *observer1 = new ObserverBlog("hello",blog);
    blog->Attach(observer1);
    blog->SetStatus("发表博客!");
    blog->Notify();
    system("pause");
    //delete blog;
    //delete observer1;
    return 0;

 

 

posted @ 2013-12-26 15:34  onlycxue  阅读(2488)  评论(1编辑  收藏  举报