when trying to use a service in drupal actually there is 3 ways , what is the preferred way to use a service and why :

  1. passing dependencies directly through the constructor:

    public function __construct(AccountProxyInterface $current_user) {
  2. passing the dependencies through the create() method wich look to me the same as injecting it through the __construct(), with the only difference , an instance will be created eah time (no singleton design pattern - not same instance will be reused)

      public static function create(ContainerInterface $container)
    //1.getting service from the service container.
    $Door = $container->get('custom_service.door');
    //2.create a new object of current class, and Inject the dependency  object into the constructor
    return new static($Door);

  //constructor receive the dependency set by the create() method
  public function __construct(Door $Door)
  1. just get get the service from the service container and no need to inject it using :
    $Door = \Drupal::service('custom_service.door')
  • 4
    You should always inject your arguments and typehint them to their interface counterpart whenever possible. Assigning instance variables from the global container is not advised. \Drupal::service... is largely used from procedural code when not in an OOP context.
    – Kevin
    Commented Jan 15, 2020 at 21:47
  • 5
    2. also has a specific context in Drupal, it is a factory method pattern used to instantiate controllers and plugins. So there is no preferred way, each one is used in a different context.
    – 4uk4
    Commented Jan 15, 2020 at 22:09
  • @4k4 can you explain the diffent contexts, so that I know when to use create factory method and when to inject directly into the constructor. Commented Jan 15, 2020 at 23:28

1 Answer 1

  1. The standard way to inject services in other services is passing dependencies directly through the constructor:


        class: Drupal\mymodule\FooService
        arguments: ['@current_user']
  2. While you can define a factory method in *.services.yml, see https://symfony.com/doc/current/service_container/factories.html, in Drupal the most common places for this are Controllers and Plugins which implement ContainerInjectionInterface::create or ContainerFactoryPluginInterface::create. See How do I use dependency injection on \Drupal::moduleHandler() to a Controller?

  3. \Drupal::service... is largely used from procedural code when not in an OOP context, like hooks or static callbacks. See the comment from @Kevin.

  • 1
    Also worth metion that you can inject dependencies (services or parameters) to a class that is not a service and will be used on procedural code like hooks by making your class implement \Drupal\Core\DependencyInjection\ContainerInjectionInterface and by calling it in your hook using $instance = \Drupal::classResolver('\Drupal\my_module\MyAwesomeClass');. Is not a service but will use services though.
    – d70rr3s
    Commented Jan 16, 2020 at 9:07
  • Is the linked question 226997 still a recommended pattern? According to this blog post the constructor should be considered internal and subject to changes.
    – Hudri
    Commented Jan 16, 2020 at 9:47
  • @Hudri, this is a good point, although it's not that you shouldn't use the design pattern anymore, it's about how you can extend existing controllers which are built with this design pattern.
    – 4uk4
    Commented Jan 16, 2020 at 10:14
  • 1
    For my own understanding: If I'm writing my own standalone class -> __construct(Services...) OK. As soon as I'm extending from another class like e.g. ControllerBase or PluginBase -> better leave the constructor alone and $container->get() the service inside create()?
    – Hudri
    Commented Jan 16, 2020 at 10:35
  • No, the linked blog post is not about writing a new controller or plugin by extending a base class in your own module, it's about extending existing core/contrib controllers and plugins.
    – 4uk4
    Commented Jan 16, 2020 at 10:57

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