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    <p>There is a lot of different implementations possible (whatever the language), but the abstract idea is :</p> <ol> <li>have an event type identifier to know wich events have been fired by the observed object (it can be whatever works);</li> <li>have a list of observers (or several, one by event type?) registered in the registered objects - that suppose that the observers are functors (function pointer or object that act like a function) or are objects with a known interface (with a virtual method to call ion event fired);</li> <li>when an event is fired (by calling a function on the observed object) we just go through the list of observers registered for the event's type and pass the event information (id plus maybe data ) to the observer to be processed;</li> </ol> <p>Here is a simplist implementation :</p> <pre><code>enum EventType { Event_A, Event_B, }; class Observer // for this example i'll suppose observer inherits this class { virtual void catchEvent( EventType e ) = 0; // for sake of the example I just need the event type, not the data, but it's often required virtual ~Observer(){}; // virtual base classes require this to work fine. }; class Observed { typedef std::vector&lt;Observer*&gt; ObserverList; typedef std::map&lt; EventType, ObserverList &gt; ObserversTable; ObserversTable m_observers; // we have observers for each event type public: void addObserver( Observer&amp; observer, EventType eType ) { m_observers[ eType ].push_back( observer ); } // this is simplist, to say the least... void sendEvent( EventType event ) // here we send the event, it will be catched by observers { // note : often this type of system is "buffered", but here we will process it immediatly as it's a simple example ObserverList&amp; observers = m_observers[ event ]; for ( ObserverList::iterator it = observers.begin(); it != observers.end(); ++it ) { Observer* observer = *it; observer-&gt;catchEvent( event ); // here an observer receive the event } } }; </code></pre> <p>It's really a basic example but that might help you understand the idea.</p>
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    1. POWhat are the principles of an event system in C++?
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    1. COThank you : it doesn't quite understand my question, but it'll be very helpful too.
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    2. COIt don't answer directly because as I said : There is a lot of different implementations possible (whatever the language) I've implemented tons of radically different way to do it in C++ only (and other variants in other languages) and it's hard to use a specific implementation for everything. Or maybe I didn't understood the exact point of your question? :)
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    3. CO@Raveline: have another look, it does answer your question: instead of using function pointers, inherit from an interface (Observer). Then it shows how to manage dynamically what kind of stuff should be done.
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