--- /dev/null
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Serializer\Normalizer;
+
+trait ObjectToPopulateTrait
+{
+ /**
+ * Extract the `object_to_populate` field from the context if it exists
+ * and is an instance of the provided $class.
+ *
+ * @param string $class The class the object should be
+ * @param $context The denormalization context
+ * @param string $key They in which to look for the object to populate.
+ * Keeps backwards compatibility with `AbstractNormalizer`.
+ *
+ * @return object|null an object if things check out, null otherwise
+ */
+ protected function extractObjectToPopulate($class, array $context, $key = null)
+ {
+ $key = $key ?: 'object_to_populate';
+
+ if (isset($context[$key]) && is_object($context[$key]) && $context[$key] instanceof $class) {
+ return $context[$key];
+ }
+
+ return null;
+ }
+}