FieldNormalizer.php

<?php

namespace Drupal\serialization\Normalizer;

use Drupal\Core\Field\FieldItemListInterface;
use Symfony\Component\Serializer\Exception\InvalidArgumentException;
use Symfony\Component\Serializer\Exception\UnexpectedValueException;
use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;

/**
 * Denormalizes data to Drupal field values.
 *
 * This class simply calls denormalize() on the individual FieldItems. The
 * FieldItem normalizers are responsible for setting the field values for each
 * item.
 *
 * @see \Drupal\serialization\Normalizer\FieldItemNormalizer.
 */
class FieldNormalizer extends ListNormalizer implements DenormalizerInterface {
  
  /**
   * {@inheritdoc}
   */
  public function denormalize($data, $class, $format = NULL, array $context = []) : mixed {
    if (!isset($context['target_instance'])) {
      throw new InvalidArgumentException('$context[\'target_instance\'] must be set to denormalize with the FieldNormalizer');
    }
    if ($context['target_instance']->getParent() == NULL) {
      throw new InvalidArgumentException('The field passed in via $context[\'target_instance\'] must have a parent set.');
    }
    /** @var \Drupal\Core\Field\FieldItemListInterface $items */
    $items = $context['target_instance'];
    $item_class = $items->getItemDefinition()
      ->getClass();
    if (!is_array($data)) {
      throw new UnexpectedValueException(sprintf('Field values for "%s" must use an array structure', $items->getName()));
    }
    foreach ($data as $item_data) {
      // Create a new item and pass it as the target for the unserialization of
      // $item_data. All items in field should have removed before this method
      // was called.
      // @see \Drupal\serialization\Normalizer\ContentEntityNormalizer::denormalize().
      $context['target_instance'] = $items->appendItem();
      $this->serializer
        ->denormalize($item_data, $item_class, $format, $context);
    }
    return $items;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getSupportedTypes(?string $format) : array {
    return [
      FieldItemListInterface::class => TRUE,
    ];
  }

}