Use event listener and custom event trigger

Author: voronkovich

app/config/services.yml

@@ -31,9 +31,15 @@ services:
         tags:
             - { name: kernel.event_listener, event: kernel.request, method: onKernelRequest }
 
-    # Event subscribers are similar to event listeners but they don't need to add
-    # a separate tag for each listened event. Instead, the PHP class of the event
-    # subscriber includes a method that returns the list of listened events.
+    app.comment_notification:
+        class: AppBundle\EventListener\CommentNotificationListener
+        arguments: ['@mailer', '@router', '@translator', '%app.notifications.email_sender%']
+        tags:
+            - { name: kernel.event_listener, event: comment.created, method: onCommentCreated }
+
+    # Event subscribers are similar to event listeners but they don't need service tags.
+    # Instead, the PHP class of the event subscriber includes a method that returns
+    # the list of events listened by that class.
     # See http://symfony.com/doc/current/event_dispatcher.html#creating-an-event-subscriber
     app.console_subscriber:
         class: AppBundle\EventListener\ConsoleEventSubscriber

src/AppBundle/Controller/BlogController.php

@@ -13,16 +13,17 @@
 
 use AppBundle\Entity\Comment;
 use AppBundle\Entity\Post;
+use AppBundle\Events;
 use AppBundle\Form\CommentType;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Cache;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Method;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Security;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
+use Symfony\Component\EventDispatcher\GenericEvent;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 
 /**
  * Controller used to manage blog contents in the public part of the site.
@@ -97,7 +98,11 @@ public function commentNewAction(Request $request, Post $post)
             $entityManager->persist($comment);
             $entityManager->flush();
 
-            $this->notifyAuthorAboutNewComment($comment);
+            // See http://symfony.com/doc/current/components/event_dispatcher/generic_event.html
+            $event = new GenericEvent($comment);
+
+            // See http://symfony.com/doc/current/components/event_dispatcher.html
+            $this->get('event_dispatcher')->dispatch(Events::COMMENT_CREATED, $event);
 
             return $this->redirectToRoute('blog_post', ['slug' => $post->getSlug()]);
         }
@@ -108,33 +113,6 @@ public function commentNewAction(Request $request, Post $post)
         ]);
     }
 
-    private function notifyAuthorAboutNewComment(Comment $comment)
-    {
-        $post = $comment->getPost();
-
-        $linkToPost = $this->generateUrl('blog_post', ['slug' => $post->getSlug()], UrlGeneratorInterface::ABSOLUTE_URL);
-
-        $translator = $this->get('translator');
-
-        $subject = $translator->trans('post.recieved_comment');
-        $body = $translator->trans('post.recieved_comment_message', [
-            '%title%' => $post->getTitle(),
-            '%link%' => $linkToPost.'#comment_'.$comment->getId(),
-        ]);
-
-        // See http://symfony.com/doc/current/email.html#sending-emails
-        $message = \Swift_Message::newInstance()
-            ->setSubject($subject)
-            ->setTo($post->getAuthorEmail())
-            ->setFrom('symfony-demo@localhost')
-            ->setBody($body, 'text/html')
-        ;
-
-        // You can view a sent email in the debug toolbar
-        // See http://symfony.com/doc/current/email/dev_environment.html#viewing-from-the-web-debug-toolbar
-        $this->get('mailer')->send($message);
-    }
-
     /**
      * This controller is called directly via the render() function in the
      * blog/post_show.html.twig template. That's why it's not needed to define

src/AppBundle/EventListener/CommentNotificationListener.php

@@ -0,0 +1,89 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace AppBundle\EventListener;
+
+use Symfony\Component\EventDispatcher\GenericEvent;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Component\Translation\TranslatorInterface;
+
+/**
+ * Notifies post's author about new comments.
+ *
+ * @author Oleg Voronkovich <oleg-voronkovich@yandex.ru>
+ */
+class CommentNotificationListener
+{
+    /**
+     * @var \Swift_Mailer
+     */
+    private $mailer;
+
+    /**
+     * @var TranslatorInterface
+     */
+    private $translator;
+
+    /**
+     * @var UrlGeneratorInterface
+     */
+    private $urlGenerator;
+
+    /**
+     * @var string
+     */
+    private $sender;
+
+    /**
+     * Constructor.
+     *
+     * @param \Swift_Mailer         $mailer
+     * @param UrlGeneratorInterface $urlGenerator
+     * @param TranslatorInterface   $translator
+     * @param string|null           $sender
+     */
+    public function __construct(\Swift_Mailer $mailer, UrlGeneratorInterface $urlGenerator, TranslatorInterface $translator, $sender = null)
+    {
+        $this->mailer = $mailer;
+        $this->urlGenerator = $urlGenerator;
+        $this->translator = $translator;
+        $this->sender = null === $sender ? 'symfony-demo@localhost' : $sender;
+    }
+
+    /**
+     * @param GenericEvent $event
+     */
+    public function onCommentCreated(GenericEvent $event)
+    {
+        $comment = $event->getSubject();
+        $post = $comment->getPost();
+
+        $linkToPost = $this->urlGenerator->generate('blog_post', ['slug' => $post->getSlug()], UrlGeneratorInterface::ABSOLUTE_URL);
+
+        $subject = $this->translator->trans('post.recieved_comment');
+        $body = $this->translator->trans('post.recieved_comment_message', [
+            '%title%' => $post->getTitle(),
+            '%link%' => $linkToPost.'#comment_'.$comment->getId(),
+        ]);
+
+        // See http://symfony.com/doc/current/email.html#sending-emails
+        $message = \Swift_Message::newInstance()
+            ->setSubject($subject)
+            ->setTo($post->getAuthorEmail())
+            ->setFrom($this->sender)
+            ->setBody($body, 'text/html')
+        ;
+
+        // You can view a sent email in the debug toolbar
+        // See http://symfony.com/doc/current/email/dev_environment.html#viewing-from-the-web-debug-toolbar
+        $this->mailer->send($message);
+    }
+}

src/AppBundle/Events.php

@@ -0,0 +1,29 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace AppBundle;
+
+/**
+ * Contains all events thrown in the Symfony demo application.
+ *
+ * @author Oleg Voronkovich <oleg-voronkovich@yandex.ru>
+ */
+final class Events
+{
+    /**
+     * See http://symfony.com/doc/current/components/event_dispatcher.html#naming-conventions.
+     *
+     * @Event("Symfony\Component\EventDispatcher\GenericEvent")
+     *
+     * @var string
+     */
+    const COMMENT_CREATED = 'comment.created';
+}