feature #977 Feature: update events sf43 (ayshiff)

This PR was squashed before being merged into the master branch (closes #977).

Discussion
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Feature: update events sf43

This PR updates the way events are used since Symfony 4.3 Beta 2 [#975](#975)

- removed Event class
- created a `CommentCreatedEvent` event object
- update calls to dispatch()
- used `Symfony\Contracts\EventDispatcher\Event` instead of the `Event` class

I have a problem when I update the calls to dispatch() to remove the event name. The `comment.created` event is inside the `not called listeners` but it works fine when I keep the event name.
I don't know if it is an issue or not.

Commits
-------

6481025 Feature: update events sf43

Author: javiereguiluz

composer.json

@@ -88,5 +88,6 @@
             "allow-contrib": true,
             "require": "4.3.*"
         }
-    }
+    },
+    "minimum-stability": "beta"
 }

src/Controller/BlogController.php

@@ -13,7 +13,7 @@
 
 use App\Entity\Comment;
 use App\Entity\Post;
-use App\Events;
+use App\Events\CommentCreatedEvent;
 use App\Form\CommentType;
 use App\Repository\PostRepository;
 use App\Repository\TagRepository;
@@ -22,7 +22,6 @@
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
-use Symfony\Component\EventDispatcher\GenericEvent;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Annotation\Route;
@@ -109,14 +108,17 @@ public function commentNew(Request $request, Post $post, EventDispatcherInterfac
             // to pass some PHP variables. For more complex applications, define your
             // own event object classes.
             // See https://symfony.com/doc/current/components/event_dispatcher/generic_event.html
-            $event = new GenericEvent($comment);
+
+            // Since Symfony 4.3, it is better to use event object to make the calls to dispatch lighter
+            // https://symfony.com/blog/new-in-symfony-4-3-simpler-event-dispatching
+            $event = new CommentCreatedEvent($comment);
 
             // When an event is dispatched, Symfony notifies it to all the listeners
             // and subscribers registered to it. Listeners can modify the information
             // passed in the event and they can even modify the execution flow, so
             // there's no guarantee that the rest of this controller will be executed.
             // See https://symfony.com/doc/current/components/event_dispatcher.html
-            $eventDispatcher->dispatch($event, Events::COMMENT_CREATED);
+            $eventDispatcher->dispatch($event);
 
             return $this->redirectToRoute('blog_post', ['slug' => $post->getSlug()]);
         }

src/EventSubscriber/CommentNotificationSubscriber.php

@@ -12,9 +12,8 @@
 namespace App\EventSubscriber;
 
 use App\Entity\Comment;
-use App\Events;
+use App\Events\CommentCreatedEvent;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
-use Symfony\Component\EventDispatcher\GenericEvent;
 use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 use Symfony\Component\Translation\TranslatorInterface;
 
@@ -41,14 +40,14 @@ public function __construct(\Swift_Mailer $mailer, UrlGeneratorInterface $urlGen
     public static function getSubscribedEvents(): array
     {
         return [
-            Events::COMMENT_CREATED => 'onCommentCreated',
+            CommentCreatedEvent::class => 'onCommentCreated',
         ];
     }
 
-    public function onCommentCreated(GenericEvent $event): void
+    public function onCommentCreated(CommentCreatedEvent $event): void
     {
         /** @var Comment $comment */
-        $comment = $event->getSubject();
+        $comment = $event->getComment();
         $post = $comment->getPost();
 
         $linkToPost = $this->urlGenerator->generate('blog_post', [

src/Events.php

@@ -0,0 +1,34 @@
+<?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 App\Events;
+
+use App\Entity\Comment;
+use Symfony\Contracts\EventDispatcher\Event;
+
+/**
+ * The comment.created event is dispatched each time a comment is created
+ * in the system.
+ */
+class CommentCreatedEvent extends Event
+{
+    protected $comment;
+
+    public function __construct(Comment $comment)
+    {
+        $this->comment = $comment;
+    }
+
+    public function getComment()
+    {
+        return $this->comment;
+    }
+}