Cover of the book Symfony 5: The Fast Track

Symfony 5: The Fast Track is the best book to learn modern Symfony development, from zero to production. +300 pages showcasing Symfony with Docker, APIs, queues & async tasks, Webpack, SPAs, etc.


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The Container Aware Event Dispatcher

The Container Aware Event Dispatcher

New in version 3.3: The ContainerAwareEventDispatcher class has been deprecated in Symfony 3.3 and it will be removed in Symfony 4.0. Use EventDispatcher with closure-proxy injection instead.


The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher is a special EventDispatcher implementation which is coupled to the service container that is part of the DependencyInjection component. It allows services to be specified as event listeners making the EventDispatcher extremely powerful.

Services are lazy loaded meaning the services attached as listeners will only be created if an event is dispatched that requires those listeners.


Setup is straightforward by injecting a Symfony\Component\DependencyInjection\ContainerInterface into the Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher:

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher;

$container = new ContainerBuilder();
$dispatcher = new ContainerAwareEventDispatcher($container);

Adding Listeners

The ContainerAwareEventDispatcher can either load specified services directly or services that implement Symfony\Component\EventDispatcher\EventSubscriberInterface.

The following examples assume the service container has been loaded with any services that are mentioned.


Services must be marked as public in the container.

Adding Services

To connect existing service definitions, use the addListenerService() method where the $callback is an array of array($serviceId, $methodName):

$dispatcher->addListenerService($eventName, array('foo', 'logListener'));

Adding Subscriber Services

Event subscribers can be added using the addSubscriberService() method where the first argument is the service ID of the subscriber service, and the second argument is the service’s class name (which must implement Symfony\Component\EventDispatcher\EventSubscriberInterface) as follows:


The EventSubscriberInterface is exactly as you would expect:

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\KernelEvents;
// ...

class StoreSubscriber implements EventSubscriberInterface
    public static function getSubscribedEvents()
        return array(
            KernelEvents::RESPONSE => array(
                array('onKernelResponsePre', 10),
                array('onKernelResponsePost', 0),
            'store.order'     => array('onStoreOrder', 0),

    public function onKernelResponsePre(FilterResponseEvent $event)
        // ...

    public function onKernelResponsePost(FilterResponseEvent $event)
        // ...

    public function onStoreOrder(FilterOrderEvent $event)
        // ...

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.