Drupal Services & Dependency Injection

Core Principle

Never use \Drupal::service() in classes — inject via constructor.

Dependency Injection Patterns

Controllers & Forms (ContainerInjectionInterface)

use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

final class MyController implements ContainerInjectionInterface {
  public function __construct(
    private readonly AccountProxyInterface $currentUser,
    private readonly EntityTypeManagerInterface $entityTypeManager,
  ) {}

  public static function create(ContainerInterface $container): static {
    return new static(
      $container->get('current_user'),
      $container->get('entity_type.manager'),
    );
  }
}

Plugins (ContainerFactoryPluginInterface)

use Drupal\Core\Plugin\ContainerFactoryPluginInterface;

final class MyBlock extends BlockBase implements ContainerFactoryPluginInterface {
  public function __construct(
    array $configuration,
    string $plugin_id,
    mixed $plugin_definition,
    private readonly EntityTypeManagerInterface $entityTypeManager,
  ) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition): static {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('entity_type.manager'),
    );
  }
}

Service Definition (services.yml)

services:
  my_module.my_service:
    class: Drupal\my_module\Service\MyService
    arguments:
      - '@entity_type.manager'
      - '@current_user'
      - '@logger.factory'

  # With autowiring (Drupal 10.3+)
  Drupal\my_module\Hook\MyModuleHooks:
    autowire: true

Common Service IDs

StringTranslationTrait

Add use StringTranslationTrait; to classes that need $this->t() without full DI of the translation service.

Generating Services with Drush

drush generate service --answers='{
  "module": "my_module",
  "service_name": "my_module.helper",
  "class": "HelperService",
  "services": ["entity_type.manager", "logger.factory"]
}'