Symfony2 Components - The Event Dispatcher

Matt Agar
Technical Director at August
matt.agar@august.com.au

“...the foundation of the Symfony
full-stack framework, but they can
also be used standalone even if you
don't use the framework...”
symfony.com/components

BrowserKit, ClassLoader, Config, Console,
CssSelector, Debug, DependencyInjection,
DomCrawler, EventDispatcher,
ExpressionLanguage, Filesystem, Finder, Form,
HttpFoundation, HttpKernel, Locale, Intl, Icu,
OptionsResolver, Process, PropertyAccess,
Routing, Security, Serializer, Stopwatch,
Templating, Translation, Validator, Yaml

Sculpin, Symfony Full Stack,
phpBB, Drupal, Thelia,
phpspec, Silex, Behat,
Guzzle, Laravel,
phpDocumentor, Carew

// Clone directly from github.com/symfony/EventDispatcher
$ git clone https://github.com/symfony/EventDispatcher.git

// Install using Composer
$ curl -s http://getcomposer.org/installer | php
$ php composer.phar require symfony/event-dispatcher

Events
The Dispatcher
Listeners

Instances of
Symfony/Component/EventDispatcher/Event

kernel.request
kernel.response
form.bind
form.post_set_data
console.command
console.exception

namespace AcmeStoreBundle;
final class StoreEvents
{
/**
* The store.order event is thrown each time an order is created
* in the system.
*/
const STORE_ORDER = 'store.order';
}

No need for
Event objects
$dispatcher->dispatch('store.order');

namespace AcmeStoreBundleEvent;
use SymfonyComponentEventDispatcherEvent;
use AcmeStoreBundleOrder;
class StoreOrderEvent extends Event {
protected $order;
public function __construct(Order $order) {
$this->order = $order;
}
public function getOrder() {
return $this->order;
}
}

$event->stopPropagation();
$event->isPropagationStopped();

SymfonyComponentEventDispatcher
GenericEvent

use SymfonyComponentEventDispatcherGenericEvent;
$storeOrderEvent = new GenericEvent(
$order,
array('a' => 'b', 'c' => 0)
);
// Implements ArrayAccess and IteratorAggregate
echo $event['a'];
$order === $storeOrderEvent->getSubject();

use SymfonyComponentEventDispatcherEventDispatcher;
$dispatcher = new EventDispatcher();

// access the dispatcher service in a controller
$dispatcher = $this->container->get('event_dispatcher');

# app/config/config.yml
services:
event_generator:
class: AcmeHelloBundleEventGenerator
arguments: ["@event_dispatcher"]

namespace AcmeHelloBundle;
use SymfonyComponentEventDispatcherEventDispatcherInterface;
class EventGenerator
{
protected $dispatcher;
public function __construct(EventDispatcherInterface $dispatcher)
{
$this->dispatcher = $dispatcher;
}
}

// event name only
$dispatcher->dispatch('store.order');
// create the StoreOrderEvent and dispatch it
$event = new StoreOrderEvent($order);
$dispatcher->dispatch(StoreEvents::STORE_ORDER, $event);

$a = $dispatcher->dispatch('store.event', $b);
$a === $b; // true
// returns the dispatcher created event
$dispatcher->dispatch('foo.event')->isPropagationStopped()

ImmutableEventDispatcher

ContainerAwareEventDispatcher

DebugTraceableEventDispatcher

$dispatcher->addListener(
'event.name',
$listener, // PHP callable
$priority = 0
);

services:
event_listener:
class: AcmeHelloBundleEventListener
tags:
- { name: kernel.event_listener,
event: kernel.exception,
method: onKernelException,
priority: 0 }

// Implements EventSubscriberInterface
$subscriber = new StoreSubscriber();
$dispatcher->addSubscriber($subscriber);

class StoreSubscriber implements EventSubscriberInterface {
public static function getSubscribedEvents() {
return array(
'kernel.request' => 'onKernelRequest',
'store.order' => array('onStoreOrder', 5),
'kernel.response' => array(
array('onKernelResponsePre', 10),
array('onKernelResponsePost', 0),
)
);
}
}

services:
event_listener:
class: AcmeHelloBundleEventSubscriber
tags:
- { name: kernel.event_subscriber }

// Event name and the dispatcher passed to listener
public function onStoreOrder(
Event $event,
$eventName,
EventDispatcherInterface $eventDispatcher
)

Symfony2 Components - The Event Dispatcher

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