EventsExampleSubscriber.php

<?php

namespace Drupal\events_example\EventSubscriber;

use Drupal\events_example\Event\IncidentEvents;
use Drupal\events_example\Event\IncidentReportEvent;
use Drupal\Core\Messenger\MessengerTrait;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * Subscribe to IncidentEvents::NEW_REPORT events and react to new reports.
 *
 * In this example we subscribe to all IncidentEvents::NEW_REPORT events and
 * point to two different methods to execute when the event is triggered. In
 * each method we have some custom logic that determines if we want to react to
 * the event by examining the event object, and the displaying a message to the
 * user indicating whether or not that method reacted to the event.
 *
 * By convention, classes subscribing to an event live in the
 * Drupal/{module_name}/EventSubscriber namespace.
 *
 * @ingroup events_example
 */
class EventsExampleSubscriber implements EventSubscriberInterface {
    use StringTranslationTrait;
    use MessengerTrait;
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() {
        // Return an array of events that you want to subscribe to mapped to the
        // method on this class that you would like called whenever the event is
        // triggered. A single class can subscribe to any number of events. For
        // organization purposes it's a good idea to create a new class for each
        // unique task/concept rather than just creating a catch-all class for all
        // event subscriptions.
        //
        // See EventSubscriberInterface::getSubscribedEvents() for an explanation
        // of the array's format.
        //
        // The array key is the name of the event your want to subscribe to. Best
        // practice is to use the constant that represents the event as defined by
        // the code responsible for dispatching the event. This way, if, for
        // example, the string name of an event changes your code will continue to
        // work. You can get a list of event constants for all events triggered by
        // core here:
        // https://api.drupal.org/api/drupal/core%21core.api.php/group/events/8.2.x.
        //
        // Since any module can define and trigger new events there may be
        // additional events available in your application. Look for classes with
        // the special @Event docblock indicator to discover other events.
        //
        // For each event key define an array of arrays composed of the method names
        // to call and optional priorities. The method name here refers to a method
        // on this class to call whenever the event is triggered.
        $events[IncidentEvents::NEW_REPORT][] = [
            'notifyMario',
        ];
        // Subscribers can optionally set a priority. If more than one subscriber is
        // listening to an event when it is triggered they will be executed in order
        // of priority. If no priority is set the default is 0.
        $events[IncidentEvents::NEW_REPORT][] = [
            'notifyBatman',
            -100,
        ];
        // We'll set an event listener with a very low priority to catch incident
        // types not yet defined. In practice, this will be the 'cat' incident.
        $events[IncidentEvents::NEW_REPORT][] = [
            'notifyDefault',
            -255,
        ];
        return $events;
    }
    
    /**
     * If this incident is about a missing princess notify Mario.
     *
     * Per our configuration above, this method is called whenever the
     * IncidentEvents::NEW_REPORT event is dispatched. This method is where you
     * place any custom logic that you want to perform when the specific event is
     * triggered.
     *
     * These responder methods receive an event object as their argument. The
     * event object is usually, but not always, specific to the event being
     * triggered and contains data about application state and configuration
     * relative to what was happening when the event was triggered.
     *
     * For example, when responding to an event triggered by saving a
     * configuration change you'll get an event object that contains the relevant
     * configuration object.
     *
     * @param \Drupal\events_example\Event\IncidentReportEvent $event
     *   The event object containing the incident report.
     */
    public function notifyMario(IncidentReportEvent $event) {
        // You can use the event object to access information about the event passed
        // along by the event dispatcher.
        if ($event->getType() == 'stolen_princess') {
            $this->messenger()
                ->addStatus($this->t('Mario has been alerted. Thank you. This message was set by an event subscriber. See @method()', [
                '@method' => __METHOD__,
            ]));
            // Optionally use the event object to stop propagation.
            // If there are other subscribers that have not been called yet this will
            // cause them to be skipped.
            $event->stopPropagation();
        }
    }
    
    /**
     * Let Batman know about any events involving the Joker.
     *
     * @param \Drupal\events_example\Event\IncidentReportEvent $event
     *   The event object containing the incident report.
     */
    public function notifyBatman(IncidentReportEvent $event) {
        if ($event->getType() == 'joker') {
            $this->messenger()
                ->addStatus($this->t('Batman has been alerted. Thank you. This message was set by an event subscriber. See @method()', [
                '@method' => __METHOD__,
            ]));
            $event->stopPropagation();
        }
    }
    
    /**
     * Handle incidents not handled by the other handlers.
     *
     * @param \Drupal\events_example\Event\IncidentReportEvent $event
     *   The event object containing the incident report.
     */
    public function notifyDefault(IncidentReportEvent $event) {
        $this->messenger()
            ->addStatus($this->t('Thank you for reporting this incident. This message was set by an event subscriber. See @method()', [
            '@method' => __METHOD__,
        ]));
        $event->stopPropagation();
    }

}