观察者模式

#include <list>
#include <iostream>
#include <sstream>
using namespace std;

class Blog;
class Observer;
class BlogObserver;




class Observer
{
protected:
	Blog * blog;

public:
	Observer(Blog * b):blog(b){}
	virtual void update(){}
};


class Blog
{
private:
	string m_name;
	string m_content;
	list<Observer *> observer_list;

public:
	Blog(string name, string content):m_name(name),m_content(content){}
	Blog(){}
	string toString()
	{
		ostringstream oss;
		oss << m_name << " " << m_content << endl;
		return oss.str();
	}

	void pubBlog(string name, string content){
		m_name = name;
		m_content = content;

		notify();
	}

	void setOnUpdateListener(Observer * ob){
		observer_list.push_back(ob);
	}

	void notify(){
		for(list<Observer*>::iterator iter = observer_list.begin();
			iter != observer_list.end(); iter++)
		{
			(*iter)->update();
		}
	}
};

class BlogObserver : public Observer
{
public:
	BlogObserver(Blog * b):Observer(b){}
	virtual void update()
	{
		cout << "blog changed!" << endl;
		cout << blog->toString() ;
	}
};

int main()
{
	Blog * blg = new Blog();
	Observer * obs = new BlogObserver(blg);
	blg->setOnUpdateListener(obs);
	
	blg->pubBlog("Tianbei", "Hello,world");
}