CObservable.h

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/* +---------------------------------------------------------------------------+
   |          The Mobile Robot Programming Toolkit (MRPT) C++ library          |
   |                                                                           |
   |                       http://www.mrpt.org/                                |
   |                                                                           |
   |   Copyright (C) 2005-2011  University of Malaga                           |
   |                                                                           |
   |    This software was written by the Machine Perception and Intelligent    |
   |      Robotics Lab, University of Malaga (Spain).                          |
   |    Contact: Jose-Luis Blanco  <jlblanco@ctima.uma.es>                     |
   |                                                                           |
   |  This file is part of the MRPT project.                                   |
   |                                                                           |
   |     MRPT 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 3 of the License, or     |
   |     (at your option) any later version.                                   |
   |                                                                           |
   |   MRPT 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 MRPT.  If not, see <http://www.gnu.org/licenses/>.         |
   |                                                                           |
   +---------------------------------------------------------------------------+ */
#ifndef  CObservable_H
#define  CObservable_H

#include <mrpt/utils/utils_defs.h>
#include <mrpt/utils/mrptEvent.h>

namespace mrpt
{
        namespace utils
        {
                class CObserver;

                /** Inherit from this class for those objects capable of being observed by a CObserver class.
                  *
                  *  The only thing to do in your child class is to call CObservable::publishEvent() whenever needed and all the
                  *   observer classes will be notified.
                  *
                  * \note The pairs CObservable / CObserver automatically notify each other the destruction of any of them, effectively ending the subscription of events.
                  *
                  *  \sa CObserver, mrptEvent
                 * \ingroup mrpt_base_grp
                  */
                class BASE_IMPEXP CObservable
                {
                        friend class CObserver;

                public:
                        CObservable();
                        virtual ~CObservable();

                private:
                        std::set<CObserver*>  m_subscribers;
                        void internal_observer_begin(CObserver*);
                        void internal_observer_end(CObserver*);

                protected:
                        /** Called when you want this object to emit an event to all the observers currently subscribed to this object. */
                        void publishEvent(const mrptEvent &e) const;

                        /** Can be called by a derived class before preparing an event for publishing with \a publishEvent to determine if there is no one
                          *  subscribed, so it can save the wasted time preparing an event that will be not read. */
                        inline bool hasSubscribers() const { return !m_subscribers.empty(); }

                }; // End of class def.

        } // End of namespace
} // end of namespace
#endif