How can I catch a login event in a subscriber?

Question

I've got an event that is triggered on hook_user_login in a module.

$event_dispatcher = \Drupal::service('event_dispatcher');
$event_dispatcher->dispatch('mymodule_user_login', $event);

I also have a subscriber that I think should be catching this event.

public function mymodule_user_login(GetResponseEvent $event) {...

static function getSubscribedEvents() {
    $events[KernelEvents::REQUEST][] = ['mymodule_user_login', 1];
    return $events;
}

The event seems to fire when I log in, however the subscriber runs on every page load afterwards.

Do I need to somehow clear the event in the subscriber?

Answer 1

Your code is subscribing to a kernel event KernelEvents::REQUEST dispatched on every request.

But you want to subscribe to the custom event 'mymodule_user_login'. The array value is the callback method, not the event name

static function getSubscribedEvents() {
    $events['mymodule_user_login'][] = ['onUserLoginCallback', 1];
    return $events;
}

which receives the custom event object, not a core event:

public function onUserLoginCallback(MyEvent $event) {
  ...
}

BTW the dispatching code is deprecated. In Drupal 9 or higher swap both arguments:

$event_dispatcher->dispatch($event, 'mymodule_user_login');

See https://symfony.com/blog/new-in-symfony-4-3-simpler-event-dispatching