edlp_d8/core/modules/language/src/LanguageConverter.php

<?php

namespace Drupal\language;

use Drupal\Core\Language\LanguageManagerInterface;
use Drupal\Core\ParamConverter\ParamConverterInterface;
use Symfony\Component\Routing\Route;

/**
 * Converts parameters for upcasting entity IDs to full objects.
 */
class LanguageConverter implements ParamConverterInterface {

  /**
   * The language manager.
   *
   * @var \Drupal\Core\Language\LanguageManagerInterface
   */
  protected $languageManager;

  /**
   * Constructs a new LanguageConverter.
   *
   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
   *   The language manager.
   */
  public function __construct(LanguageManagerInterface $language_manager) {
    $this->languageManager = $language_manager;
  }

  /**
   * {@inheritdoc}
   */
  public function convert($value, $definition, $name, array $defaults) {
    if (!empty($value)) {
      return $this->languageManager->getLanguage($value);
    }
    return NULL;
  }

  /**
   * {@inheritdoc}
   */
  public function applies($definition, $name, Route $route) {
    return (!empty($definition['type']) && $definition['type'] == 'language');
  }

}