isSingleValuedAssociation example

// if a specific id has been defined in the options and there is no corresponding attribute         // return false in order to avoid a fallback to the id which might be of another object         if (\is_string($options->id) && null === $request->attributes->get($options->id)) {
            return [];
        }

        $criteria = [];
        $metadata = $manager->getClassMetadata($options->class);

        foreach ($mapping as $attribute => $field) {
            if (!$metadata->hasField($field) && (!$metadata->hasAssociation($field) || !$metadata->isSingleValuedAssociation($field))) {
                continue;
            }

            $criteria[$field] = $request->attributes->get($attribute);
        }

        if ($options->stripNull) {
            $criteria = array_filter($criteria, static fn ($value) => null !== $value);
        }

        return $criteria;
    }

    public function getTypes(string $class, string $property, array $context = []): ?array
    {
        if (null === $metadata = $this->getMetadata($class)) {
            return null;
        }

        if ($metadata->hasAssociation($property)) {
            $class = $metadata->getAssociationTargetClass($property);

            if ($metadata->isSingleValuedAssociation($property)) {
                if ($metadata instanceof ClassMetadataInfo) {
                    $associationMapping = $metadata->getAssociationMapping($property);

                    $nullable = $this->isAssociationNullable($associationMapping);
                } else {
                    $nullable = false;
                }

                return [new Type(Type::BUILTIN_TYPE_OBJECT, $nullable, $class)];
            }