final class IncidentEvents in Examples for Developers 8

Defines events for the events_example module.

It is best practice define the unique names for events as constants on a class. This provides a place for documentation of the events. As well as allowing the event dispatcher to use the constants instead of hard coding a string.

In this example we're defining one new event: 'events_example.new_incident_report'. This event will be dispatched by the form controller \Drupal\events_example\Form\EventsExampleForm whenever a new incident is reported. If your application dispatches more than one event you can use a single class to document multiple events. Just add a new constant for each. Group related events together with a single class, define another class for unrelated events.

The docblock for each event constant should contain an "@Event" tag. This is used to ensure documentation parsing tools can gather and list all events. For example, https://api.drupal.org/api/drupal/core%21core.api.php/group/events/

The docblock should also contain a description of when, and under what conditions, the event is triggered. A module developer should be able to read this description in order to determine whether or not this is the event that they want to subscribe to.

This class is declared as final so that it can not be extended. It should only ever be used to provide unique event names, and documentation.

In core \Drupal\Core\Config\ConfigCrudEvent is a good example of defining and documenting new events.

Hierarchy

• class \Drupal\events_example\Event\IncidentEvents

See also

\Drupal\Core\Config\ConfigCrudEvent

Related topics

Example: Events

Demonstrates subscribing to, and dispatching, events.

2 files declare their use of IncidentEvents

EventsExampleForm.php in events_example/src/Form/EventsExampleForm.php

EventsExampleSubscriber.php in events_example/src/EventSubscriber/EventsExampleSubscriber.php

File

events_example/src/Event/IncidentEvents.php, line 41

Namespace

Drupal\events_example\Event

final class IncidentEvents {

  /**
   * Name of the event fired when a new incident is reported.
   *
   * This event allows modules to perform an action whenever a new incident is
   * reported via the incident report form. The event listener method receives a
   * \Drupal\events_example\Event\IncidentReportEvent instance.
   *
   * @Event
   *
   * @see \Drupal\events_example\Event\IncidentReportEvent
   *
   * @var string
   */
  const NEW_REPORT = 'events_example.new_incident_report';

}

Members

Name	Modifiers	Type	Description	Overrides
IncidentEvents::NEW_REPORT		constant	Name of the event fired when a new incident is reported.