atelierspierrot/event-manager

The events manager package of Les Ateliers Pierrot.

v1.0.1 2016-01-01 23:25 UTC

README

Code Climate documentation The events manager package of Les Ateliers Pierrot

Installation

For a complete information about how to install this package and load its namespace, please have a look at our USAGE documentation.

If you are a Composer user, just add the package to the requirements of your project's composer.json manifest file:

"atelierspierrot/event-manager": "dev-master"

You can use a specific release or the latest release of a major version using the appropriate version constraint.

Please note that this package depends on the externals PHP Patterns and PHP Library.

SPL interfaces

As a reminder, the SPL observer objects are:

interface SplObserver {
    abstract public void update ( SplSubject $subject )
}

interface SplSubject {
    abstract public void attach ( SplObserver $observer )
    abstract public void detach ( SplObserver $observer )
    abstract public void notify ( void )
}

Basics

The basic idea of an event propagation system in PHP is quite simple:

  • an object A can trigger some events during its life-cycle (to inform about an update for instance) ;
  • an object B can adapt its properties or behaviors when the object A triggered an event (to keep the last value of a property of A for instance).

This can be implemented with an observer/observable system where the object A of the example above is observable while the B is its observer. Basically, the observable can be considered as an SplSubject as defined in the SPL interfaces above while the observer can be considered as an SplObserver. But the standard system (the SPL interfaces) only allows one single event to be triggered (or multiple events handled by the same method of the observer). We could use this basic definitions of event triggering but it forces the implementations to make a switch if the observable can trigger different events ...

The implementation in the library is ready to handle multiple events triggering allowing the observers to define the method that should be called when an event is fired. This method defaults to handleEvent(). To do so, the SplObserver interface is renamed (and rewritten) as the ObserverInterface and the SplSubject as the ObservableInterface. The event is a standalone object implementing the EventInterface:

interface ObserverInterface {
    abstract public void handleEvent ( EventInterface $event )
}

interface ObservableInterface {
    abstract public void attachObserver ( ObserverInterface $observer | array($object , $method) | $callback )
    abstract public void detachObserver ( ObserverInterface $observer | array($object , $method) | $callback )
    abstract public void triggerEvent ( $event_name )
}

interface EventInterface {
    abstract public ObservableInterface getSubject ()
    abstract public string getName ()
    abstract public void stopPropagation ()
    abstract public bool isPropagationStopped ()
}

Events manager

A kernel object is defined to handle a set of events listeners/observers for a global application: the EventManager object. It introduces two new concepts: the listeners and the subscribers.

Basically, a listener is like an observer, it references itself to the object triggering the event it want to observe, a subscriber does not references itself to each events it wants to listen, but to the global events manager, that asks it the list of events it may listen:

interface EventListenerInterface 
    extends ObserverInterface {}

interface EventSubscriberInterface {
    abstract public array getSubscribedEvents ()
}

Author & License

Event Manager

http://github.com/atelierspierrot/event-manager

Copyright (c) 2015-2016 Pierre Cassat and contributors

Licensed under the Apache 2 license.

http://www.apache.org/licenses/LICENSE-2.0

Les Ateliers Pierrot - Paris, France

http://www.ateliers-pierrot.fr/ - contact@ateliers-pierrot.fr