ExampleFieldEventSubscribers.php in Hook Event Dispatcher 3.x        
                          
                  
                        
  
  
  
  
File
  examples/ExampleFieldEventSubscribers.php
  
    View source  
  <?php
namespace Drupal\hook_event_dispatcher;
use Drupal\field_event_dispatcher\Event\Field\WidgetFormAlterEvent;
use Drupal\field_event_dispatcher\Event\Field\WidgetTypeFormAlterEvent;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
final class ExampleFieldEventSubscribers implements EventSubscriberInterface {
  
  public function alterWidgetForm(WidgetFormAlterEvent $event) : void {
    $element =& $event
      ->getElement();
    $element['extra_field'] = [
      '#type' => 'textfield',
      '#title' => 'I am an extra field!',
    ];
  }
  
  public function alterWidgetStringTextField(WidgetTypeFormAlterEvent $event) : void {
    $element =& $event
      ->getElement();
    
    $element['special_label'] = [
      'type' => 'label',
      'label' => 'Extra special label',
    ];
  }
  
  public static function getSubscribedEvents() : array {
    return [
      HookEventDispatcherInterface::WIDGET_FORM_ALTER => 'alterWidgetForm',
      'hook_event_dispatcher.widget_string_textfield.alter' => 'alterWidgetStringTextField',
    ];
  }
}