How to use dependency injection to apply a class static method?

Question

I'm building a custom form (extending ConfigFormBase) and using static method File::load($fid). How to use dependency injection to call this method? Thank you!

Answer 1

In __construct() you can implement like this:

use Drupal\Core\Entity\EntityTypeManagerInterface;

public function __construct(EntityTypeManagerInterface $entity_type_manager) {
    $this->entityTypeManager = $entity_type_manager;
}

and create() method

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

You can use this service to get the file storage:

$file_storage = $this->entityTypeManager()->getStorage('file');

and then load the file:

$file = $file_storage->load($fid);

Answer 2

This is my final code implementation as I was having this sort of warning:

Expected \Drupal\file\FileStorageInterface, got object Invocation parameter types are not compatible with declared.

So I updated create method to get the file storage directly:

class MyClassForm extends ConfigFormBase {

  /**
   * File storage for files.
   *
   * @var \Drupal\file\FileStorageInterface
   */
  protected $fileStorage;

  /**
   * SiteSettingsForm constructor.
   *
   * @param \Drupal\file\FileStorageInterface $file_storage
   *   File storage for files.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager, ConfigFactoryInterface $config_factory) {
    parent::__construct($config_factory);
    $this->fileStorage = $entity_type_manager->getStorage('file');
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static(
      $container->get('entity_type.manager'),
      $container->get('config.factory')
    );
  }
}