commerce_google_tag_manager: Example of a CheckoutOption event subscriber

CheckoutOptionSubscriber.php

use Drupal\commerce_google_tag_manager\Event\TrackCheckoutStepEvent;

<?php

class CheckoutOptionSubscriber implements EventSubscriberInterface {

  public static function getSubscribedEvents() {
	  return [
      'commerce_google_tag_manager.track_checkout_step' => 'trackUser'
    ];
  }

  public function trackUser(TrackCheckoutStepEvent $event) {
    // Only track this option for the first checkout step
    if ($event->getStepIndex() === 0) {
      $event_tracker = Drupal::service('commerce_google_tag_manager.event_tracker');
      $current_user = Drupal::service('current_user');
      $option = $current_user->isAnonymous() ? 'anonymous' : 'authenticated';
      $event_tracker->checkoutOption(0, $option);
    }
  }
}