makomweb / event-dispatcher-tutorial

How to deal with events (dispatching / subscribing / listening) in the Symfony eco system

Event dispatcher / subscriber / listener tutorial

created with

> symfony new event-dispatcher-tutorial
> composer require symfony/event-dispatcher  

Dispatch an event

class UserRegisteredEvent extends Event {
    const NAME = 'user.registered';
    protected $user;

    public function __construct(User $user) {
        $this->user = $user;
    }

    public function getUser(): User {
        return $this->user;
    }
}

public function __construct(EventDispatcherInterface $dispatcher) {

    $this->dispatcher = $dispatcher;
}

/**
 * @Route("/user", name="user")
 */
public function index(): Response {
    $user = new User();
    $user->name = "John Doe";
    $user->age = 23;

    $this->dispatcher->dispatch(new UserRegisteredEvent($user));

    // ...
}

Subscribe to an event (via EventSubscriber)

class UserEventSubscriber implements EventSubscriberInterface {
    public static function getSubscribedEvents() : array {
        return [
            UserRegisteredEvent::class => 'onRegistered'
        ];
    }

    public function onRegistered(UserRegisteredEvent $event) {
        // TODO Handle event!
    }
}

Listen to an event

class UserEventListener {
    public function onRegistered(UserRegisteredEvent $event) {
        // TODO Handle event!
    }
}

# services.yaml
App\EventListener\UserEventListener:
  tags:
    - { 'name': 'kernel.event_listener', 'event': 'App\Event\UserRegisteredEvent', 'method': 'onRegistered' }

Conclusion

Event listener and subscriber behave the same way.
It's a matter of taste how dealing with events should be configured in your modules and application.

Debugging

check if there is an event listener registered for this event

php bin/console debug:event-dispatcher