CObserver.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 <mrpt/system/mrptEvent.h>
#include <set>
 
namespace mrpt
{
namespace system
{
class CObservable;
 
/** Inherit from this class to get notified about events from any CObservable
 * object after subscribing to it.
 *
 *  The main methods in this class are:
 *   - observeBegin(): To be called to start listening at a given object.
 *   - OnEvent(): Virtual functions to be implemented in your child class to
 * receive all the notifications.
 *
 *  Note that if custom (child) mrptEvent classes are used, you can tell
 * between them in runtime with "dynamic_cast<>()".
 *
 * \note The pairs CObservable / CObserver automatically notify each other the
 * destruction of any of them, effectively ending the subscription of events.
 * \ingroup mrpt_system_grp
 *  \sa CObservable, mrptEvent
 */
class CObserver
{
        friend class CObservable;
 
   public:
        CObserver();
        virtual ~CObserver();
 
        /** Starts the subscription of this observer to the given object.  \sa
         * observeEnd  */
        void observeBegin(CObservable& obj);
 
        /** Ends the subscription of this observer to the given object (note that
           there is no need to call this method, since the destruction of the first
           of observer/observed will put an end to the process
                \sa observeBegin  */
        void observeEnd(CObservable& obj);
 
   private:
        std::set<CObservable*> m_subscribed;
        void internal_on_event(const mrptEvent& e);
 
   protected:
        /** This virtual function will be called upon receive of any event after
         * starting listening at any CObservable object.
         */
        virtual void OnEvent(const mrptEvent& e) = 0;
 
};  // End of class def.
 
}  // namespace system
}  // namespace mrpt