Re-add old blog posts from Astro

source/_posts/experimenting-events-drupal-8.md

@@ -0,0 +1,81 @@
+---
+title: Experimenting with events in Drupal 8
+date: 2018-08-21
+excerpt: Trying a different way of structuring Drupal modules, using event subscribers and autowiring.
+tags:
+    - drupal
+    - drupal-8
+    - drupal-planet
+    - php
+    - symfony
+promoted: true
+---
+
+I’ve been experimenting with moving some code to Drupal 8, and I’m quite
+intrigued by a different way that I’ve tried to structure it - using event
+subscribers, building on some of the takeaways from Drupal Dev Days.
+
+Here is how this module is currently structured:
+
+![](/images/blog/events-drupal-8/1.png){.border .p-1}
+
+Note that there is no `opdavies_blog.module` file, and rather than calling
+actions from within a hook like `opdavies_blog_entity_update()`, each action
+becomes it’s own event subscriber class.
+
+This means that there are no long `hook_entity_update` functions, and instead
+there are descriptive, readable event subscriber class names, simpler action
+code that is responsibile only for performing one task, and you’re able to
+inject and autowire dependencies into the event subscriber classes as services -
+making it easier and cleaner to use dependency injection, and simpler write
+tests to mock dependencies when needed.
+
+The additional events are provided by the
+[Hook Event Dispatcher module](https://www.drupal.org/project/hook_event_dispatcher).
+
+## Code
+
+`opdavies_blog.services.yml`:
+
+```yaml
+services:
+  Drupal\opdavies_blog\EventSubscriber\PostToMedium:
+    autowire: true
+    tags:
+      - { name: event_subscriber }
+
+  Drupal\opdavies_blog\EventSubscriber\SendTweet:
+    autowire: true
+    tags:
+      - { name: event_subscriber }
+```
+
+<div class="note" markdown="1">
+Adding `autowire: true` is not required for the event subscriber to work. I’m using it to automatically inject any dependencies into the class rather than specifying them separately as arguments.
+</div>
+
+`src/EventSubscriber/SendTweet.php`:
+
+```php
+namespace Drupal\opdavies_blog\EventSubscriber;
+
+use Drupal\hook_event_dispatcher\Event\Entity\EntityUpdateEvent;
+use Drupal\hook_event_dispatcher\HookEventDispatcherInterface;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+class SendTweet implements EventSubscriberInterface {
+
+  ...
+
+  public static function getSubscribedEvents() {
+    return [
+      HookEventDispatcherInterface::ENTITY_UPDATE => 'sendTweet',
+    ];
+  }
+
+  public function sendTweet(EntityUpdateEvent $event) {
+    // Perform checks and send the tweet.
+  }
+
+}
+```