RelationshipData example

  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 */