TraversableObjectNormalizer.php

<?php

namespace Drupal\jsonapi_test_data_type\Normalizer;

use Drupal\jsonapi_test_data_type\TraversableObject;
use Drupal\serialization\Normalizer\NormalizerBase;

/**
 * Normalizes TraversableObject.
 */
class TraversableObjectNormalizer extends NormalizerBase {
    
    /**
     * {@inheritdoc}
     */
    public function normalize($object, $format = NULL, array $context = []) : array|string|int|float|bool|\ArrayObject|null {
        return $object->property;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSupportedTypes(?string $format) : array {
        return [
            TraversableObject::class => TRUE,
        ];
    }

}