CObservable.h

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/* +---------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)               |
   |                          http://www.mrpt.org/                             |
   |                                                                           |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file        |
   | See: http://www.mrpt.org/Authors - All rights reserved.                   |
   | Released under BSD License. See details in http://www.mrpt.org/License    |
   +---------------------------------------------------------------------------+ */
#ifndef  CObservable_H
#define  CObservable_H

#include <mrpt/config.h>
#include <mrpt/base/link_pragmas.h>
#include <set>

namespace mrpt
{
        namespace utils
        {
                class CObserver;
                class mrptEvent;

                /** 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