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Autowiring

When to Use

When you want the container to automatically resolve constructor arguments based on type hints — reduces YAML boilerplate for services with many dependencies.

Steps

  1. Enable autowiring for your service 
    services:
  my_module.autowired_service:
    class: Drupal\my_module\AutowiredService
    autowire: true

Or enable for all services in the file: 

services:
  _defaults:
    autowire: true

  my_module.autowired_service:
    class: Drupal\my_module\AutowiredService

  1. Type-hint constructor parameters 

    namespace Drupal\my_module;

use Drupal\Core\Database\Connection;
use Drupal\Core\Entity\EntityTypeManagerInterface;
use Psr\Log\LoggerInterface;

class AutowiredService {

  public function __construct(
    protected Connection $database,
    protected EntityTypeManagerInterface $entityTypeManager,
    protected LoggerInterface $logger,
  ) {}
}

  2. For ambiguous interfaces, create aliases 

    services:
  # Alias tells autowire which logger to inject
  Psr\Log\LoggerInterface: '@logger.channel.my_module'

  my_module.autowired_service:
    class: Drupal\my_module\AutowiredService
    autowire: true

  3. Use #[Autowire] attribute for specific parameters (Drupal 11+ / PHP 8.1+) 

    use Symfony\Component\DependencyInjection\Attribute\Autowire;

public function __construct(
  #[Autowire(service: 'logger.channel.my_module')]
  protected LoggerInterface $logger,
) {}

Decision Points

At this step... If... Then...
Enabling autowire Service has 5+ dependencies Autowiring reduces YAML boilerplate
Enabling autowire Dependencies are core services with clear type hints Safe to autowire
Creating aliases Multiple services implement same interface Create alias for autowire to resolve
Using #[Autowire] Only 1-2 params need explicit service ID Use attribute instead of full alias definition
Choosing autowire vs explicit Service is public API Explicit arguments are clearer for documentation

Common Mistakes

  • Autowiring without type hints — Autowiring requires typed constructor parameters; remove autowire or add types
  • Expecting autowire to work for scalars — Autowiring only works for service objects, not strings/integers/parameters
  • Not creating aliases for ambiguous interfaces — If 10 services implement FooInterface, autowire can't choose
  • Autowiring in performance-critical services — Autowiring uses reflection; slight overhead (usually negligible)
  • Not testing container compilation — Autowire failures only appear at cache rebuild; test in CI
  • Using autowire for contrib/community modules — Stick to explicit arguments for public APIs; autowire is best for internal services

See Also