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Plugin Injection (ContainerFactoryPluginInterface)

When to Use

When injecting services into plugins (blocks, field formatters, field widgets, condition plugins, etc.) — plugins receive additional arguments (configuration, plugin_id, plugin_definition) that must be handled.

Steps

  1. Implement ContainerFactoryPluginInterface 

    namespace Drupal\my_module\Plugin\Block;

use Drupal\Core\Block\BlockBase;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Database\Connection;
use Psr\Log\LoggerInterface;

/**
 * @Block(
 *   id = "my_module_example",
 *   admin_label = @Translation("Example Block"),
 * )
 */
class ExampleBlock extends BlockBase implements ContainerFactoryPluginInterface {

  public function __construct(
    array $configuration,
    $plugin_id,
    $plugin_definition,
    protected Connection $database,
    protected LoggerInterface $logger,
  ) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
  }

  public static function create(
    ContainerInterface $container,
    array $configuration,
    $plugin_id,
    $plugin_definition
  ) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('database'),
      $container->get('logger.channel.my_module'),
    );
  }

  public function build() {
    return ['#markup' => 'Hello'];
  }
}

  2. Constructor Parameter Order:

  3. First 3 params: $configuration, $plugin_id, $plugin_definition (in that order)
  4. Remaining params: Your injected services
  5. Call parent::__construct() with first 3 params

Decision Points

At this step... If... Then...
Choosing parameter order Always Put $configuration, $plugin_id, $plugin_definition first (required)
Calling parent constructor Plugin extends base class (BlockBase, FormatterBase) Call parent::__construct() with plugin params
Adding services Service is required for plugin functionality Inject via constructor
Adding services Service is optional or rarely used Inject or use \Drupal::service() in method (less ideal)

Pattern

Field Formatter Example: 

namespace Drupal\my_module\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FormatterBase;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;

/**
 * @FieldFormatter(
 *   id = "my_custom_formatter",
 *   label = @Translation("My Custom Formatter"),
 *   field_types = {"string"}
 * )
 */
class MyCustomFormatter extends FormatterBase implements ContainerFactoryPluginInterface {

  public function __construct(
    $plugin_id,
    $plugin_definition,
    $field_definition,
    array $settings,
    $label,
    $view_mode,
    array $third_party_settings,
    protected EntityTypeManagerInterface $entityTypeManager,
  ) {
    parent::__construct(
      $plugin_id,
      $plugin_definition,
      $field_definition,
      $settings,
      $label,
      $view_mode,
      $third_party_settings
    );
  }

  public static function create(
    ContainerInterface $container,
    array $configuration,
    $plugin_id,
    $plugin_definition
  ) {
    return new static(
      $plugin_id,
      $plugin_definition,
      $configuration['field_definition'],
      $configuration['settings'],
      $configuration['label'],
      $configuration['view_mode'],
      $configuration['third_party_settings'],
      $container->get('entity_type.manager'),
    );
  }
}

Reference: /core/lib/Drupal/Core/Plugin/ContainerFactoryPluginInterface.php, /core/modules/system/src/Plugin/Block/SystemBrandingBlock.php (example)

Common Mistakes

  • Wrong parameter order in create() — Must be ($container, $configuration, $plugin_id, $plugin_definition)
  • Wrong parameter order in __construct() — Plugin params first, then your services
  • Not calling parent::__construct() — Parent constructor often sets critical protected properties
  • Forgetting $configuration is an array — Extract values like $configuration['settings'], not use it directly
  • Assuming $configuration structure — Different plugin types have different $configuration arrays (check parent class)

See Also