CObservable.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2018, 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 |
   +------------------------------------------------------------------------+ */
#pragma once
 
#include <set>
 
namespace mrpt
{
namespace system
{
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_system_grp
 */
class 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.
 
}  // namespace system
}  // namespace mrpt