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/*
Copyright (C) 2005-2009 Michel de Boer <michel@twinklephone.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/**
* @file
* Abstract observer pattern.
*/
#ifndef _OBSERVER_H
#define _OBSERVER_H
#include <list>
#include "threads/mutex.h"
using namespace std;
namespace patterns {
/** Observer. */
class t_observer {
public:
virtual ~t_observer() {};
/**
* This method is called by an observed subject to indicate its state
* has changed.
*/
virtual void update(void) = 0;
/**
* This method is called when the subject is destroyed.
*/
virtual void subject_destroyed(void) = 0;
};
/** An observed subject. */
class t_subject {
private:
/** Mutex to protect access to the observers. */
mutable t_recursive_mutex mtx_observers;
list<t_observer *> observers; /** Observers of this subject. */
public:
virtual ~t_subject();
/**
* Attach an observer.
* @param o [in] The observer.
*/
void attach(t_observer *o);
/**
* Detach an observer.
* @param o [in] The observer.
*/
void detach(t_observer *o);
/**
* Notify all observers.
*/
void notify(void) const;
};
}; // namespace
#endif
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