events_example.module in Examples for Developers 8

Demonstrates how to subscribe to and dispatch events.

File

events_example/events_example.module

<?php

/**
 * @file
 * Demonstrates how to subscribe to and dispatch events.
 */

/**
 * @defgroup events_example Example: Events
 * @ingroup examples
 * @{
 * Demonstrates subscribing to, and dispatching, events.
 *
 * Events allow for different components of the system to interact and
 * communicate with each other. Modules can either dispatch events, subscribe to
 * events, or both.
 *
 * Subscribing to an event allows a module to declare that it would like to be
 * notified anytime a specific event happens. A module can subscribe to any
 * number of events, and can even subscribe to the same event more than once.
 *
 * Dispatching an event allows a module, or Drupal core subsystem, to notify any
 * registered subscribers that a specific event has just taken place. When an
 * event is dispatched the registered code for each subscriber is executed. For
 * example, whenever a configuration entity is updated the Configuration API
 * dispatches a new event allowing all subscribers to react to the change.
 *
 * This allows modules to extend other systems without the need to modify the
 * original code.
 *
 * Each event has a unique string name. This string is often referred to as "the
 * event", or "the event name". This string is how you identify which event(s)
 * you are interested in. A complete list of events dispatched by core is
 * available at
 * https://api.drupal.org/api/drupal/core%21core.api.php/group/events/
 *
 * Drupal's event system is an extension of the
 * @link http://symfony.com/doc/current/components/event_dispatcher.html Symfony
 * EventDispatcher component @endlink, and implements the Mediator pattern.
 *
 * Subscribing to an event requires:
 * - Defining a service in your module, tagged with 'event_subscriber'.
 * - Defining a class for your subscriber service that implements
 *   \Symfony\Component\EventDispatcher\EventSubscriberInterface
 * - Using the getSubscribedEvents method to return a list of the events you
 *   want to subscribe to, and which methods on the class should be called for
 *   each one.
 *
 * For an example of subscribing to an event see the events_example.services.yml
 * file. And the \Drupal\events_example\EventSubscriber\EventsExampleSubscriber
 * class.
 *
 * Dispatching an event requires:
 * - Defining a new static class with constants for unique event names and
 *   documentation. Example: \Drupal\events_exampl\Event\IncidentEvents
 * - Defining an event class that extends
 *   \Symfony\Component\EventDispatcher\Event
 *   Example: \Drupal\events_example\Event\IncidentReportEvent
 * - Use the 'event_dispatcher' service in your code to dispatch an event and
 *   provide an event object as an argument. Example:
 *   \Drupal\events_example\Form\EventsExampleForm::submitForm()
 *
 * This example code is based off of the article @link
 * https://drupalize.me/blog/201502/responding-events-drupal-8 Responding to
 * Events in Drupal 8 @endlink.
 *
 * @see events
 * @see \Symfony\Component\EventDispatcher\EventDispatcherInterface
 * @see \Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher
 * @see service_tag
 */

/**
 * @} End of "defgroup events_example".
 */