class LoaderChain

LoaderChainTest.php in drupal/core/vendor/symfony/validator/Symfony/Component/Validator/Tests/Mapping/Loader/LoaderChainTest.php

ValidatorBuilder.php in drupal/core/vendor/symfony/validator/Symfony/Component/Validator/ValidatorBuilder.php

class LoaderChain implements LoaderInterface {
  protected $loaders;

  /**
   * Accepts a list of LoaderInterface instances
   *
   * @param LoaderInterface[] $loaders An array of LoaderInterface instances
   *
   * @throws MappingException If any of the loaders does not implement LoaderInterface
   */
  public function __construct(array $loaders) {
    foreach ($loaders as $loader) {
      if (!$loader instanceof LoaderInterface) {
        throw new MappingException(sprintf('Class %s is expected to implement LoaderInterface', get_class($loader)));
      }
    }
    $this->loaders = $loaders;
  }

  /**
   * {@inheritDoc}
   */
  public function loadClassMetadata(ClassMetadata $metadata) {
    $success = false;
    foreach ($this->loaders as $loader) {
      $success = $loader
        ->loadClassMetadata($metadata) || $success;
    }
    return $success;
  }

}