getFieldByInternalName example

  protected function getRelatableResourceTypes(array $resource_types, array $definitions) {
    $relatable_resource_types = [];
    foreach ($resource_types as $resource_type) {
      $definition = $definitions[$resource_type->getTypeName()];
      $resource_type_field = $resource_type->getFieldByInternalName($definition->getFieldDefinition()->getName());
      if ($resource_type_field instanceof ResourceTypeRelationship) {
        foreach ($resource_type_field->getRelatableResourceTypes() as $relatable_resource_type) {
          $relatable_resource_types[$relatable_resource_type->getTypeName()] = $relatable_resource_type;
        }
      }
    }
    return $relatable_resource_types;
  }

  /** * Whether the given resources can be traversed to other resources. * * @param \Drupal\jsonapi\ResourceType\ResourceType[] $resource_types * The resources types to evaluate. * * @return bool * TRUE if any one of the given resource types is traversable. * * @todo This class shouldn't be aware of entity types and their definitions. * Whether a resource can have relationships to other resources is information * we ought to be able to discover on the ResourceType. However, we cannot * reliably determine this information with existing APIs. Entities may be * backed by various storages that are unable to perform queries across * references and certain storages may not be able to store references at all. */

  public function getFieldByPublicName($public_field_name) {
    return isset($this->fieldMapping[$public_field_name])
      ? $this->getFieldByInternalName($this->fieldMapping[$public_field_name])
      : NULL;
  }

  /** * Gets a particular attribute or relationship field by internal field name. * * @param string $internal_field_name * The internal field name of the desired field. * * @return \Drupal\jsonapi\ResourceType\ResourceTypeField|null * A resource type field object or NULL if the field does not exist on this * resource type. */

class FieldNormalizer extends NormalizerBase implements DenormalizerInterface {

  /** * {@inheritdoc} */
  public function normalize($field, $format = NULL, array $context = []): array|string|int|float|bool|\ArrayObject|NULL {
    /** @var \Drupal\Core\Field\FieldItemListInterface $field */
    $normalized_items = $this->normalizeFieldItems($field, $format, $context);
    assert($context['resource_object'] instanceof ResourceObject);
    return $context['resource_object']->getResourceType()->getFieldByInternalName($field->getName())->hasOne()
      ? array_shift($normalized_items) ?: CacheableNormalization::permanent(NULL)
      : CacheableNormalization::aggregate($normalized_items);
  }

  /** * {@inheritdoc} */
  public function denormalize($data, $class, $format = NULL, array $context = []): mixed {
    $field_definition = $context['field_definition'];
    assert($field_definition instanceof FieldDefinitionInterface);
    $resource_type = $context['resource_type'];
    

  public function normalize($field, $format = NULL, array $context = []): array|string|int|float|bool|\ArrayObject|NULL {
    assert($field instanceof EntityReferenceFieldItemListInterface);
    // Build the relationship object based on the Entity Reference and normalize     // that object instead.     $resource_identifiers = array_filter(ResourceIdentifier::toResourceIdentifiers($field->filterEmptyItems()), function DResourceIdentifierInterface $resource_identifier) {
      return !$resource_identifier->getResourceType()->isInternal();
    });
    $normalized_items = CacheableNormalization::aggregate($this->serializer->normalize($resource_identifiers, $format, $context));
    assert($context['resource_object'] instanceof ResourceObject);
    $resource_relationship = $context['resource_object']->getResourceType()->getFieldByInternalName($field->getName());
    assert($resource_relationship instanceof ResourceTypeRelationship);
    $link_cacheability = new CacheableMetadata();
    $links = array_map(function DUrl $link) use ($link_cacheability) {
      $href = $link->setAbsolute()->toString(TRUE);
      $link_cacheability->addCacheableDependency($href);
      return ['href' => $href->getGeneratedUrl()];
    }, static::getRelationshipLinks($context['resource_object'], $resource_relationship));
    $data_normalization = $normalized_items->getNormalization();
    $normalization = [
      // Empty 'to-one' relationships must be NULL.       // Empty 'to-many' relationships must be an empty array.

$file = $this->fileUploader->handleFileUploadForField($field_definition, $filename, $this->currentUser);

    if ($file instanceof EntityConstraintViolationListInterface) {
      $violations = $file;
      $message = "Unprocessable Entity: file validation failed.\n";
      $message .= implode("\n", array_map(function DConstraintViolationInterface $violation) {
        return PlainTextOutput::renderFromHtml($violation->getMessage());
      }, (array) $violations->getIterator()));
      throw new UnprocessableEntityHttpException($message);
    }

    if ($resource_type->getFieldByInternalName($file_field_name)->hasOne()) {
      $entity->{$file_field_name} = $file;
    }
    else {
      $entity->get($file_field_name)->appendItem($file);
    }
    static::validate($entity, [$file_field_name]);
    $entity->save();

    $route_parameters = ['entity' => $entity->uuid()];
    $route_name = sprintf('jsonapi.%s.%s.related', $resource_type->getTypeName(), $resource_type->getPublicName($file_field_name));
    $related_url = Url::fromRoute($route_name, $route_parameters)->toString(TRUE);
    

  public static function createFromEntityReferenceField(ResourceObject $context, EntityReferenceFieldItemListInterface $field, LinkCollection $links = NULL, array $meta = []) {
    $context_resource_type = $context->getResourceType();
    $resource_field = $context_resource_type->getFieldByInternalName($field->getName());
    return new static(
      $resource_field->getPublicName(),
      new RelationshipData(ResourceIdentifier::toResourceIdentifiers($field), $resource_field->hasOne() ? 1 : -1),
      static::buildLinkCollectionFromEntityReferenceField($context, $field, $links ?: new LinkCollection([])),
      $meta,
      $context
    );
  }

  /** * Gets context resource object of the relationship. * * @return \Drupal\jsonapi\JsonApiResource\ResourceObject * The context ResourceObject. * * @see \Drupal\jsonapi\JsonApiResource\Relationship::$context */