How to use it?

[deadpony]

just how to use it?

[cv65kr]

For more complex example, just look at Sylius Repositories.

https://github.com/Sylius/Sylius/blob/dcc4acd46a3b9d629bb6f7456d7d16dae738988d/src/Sylius/Bundle/CoreBundle/Doctrine/ORM/OrderRepository.php

First step:

    /** @var AssociationHydrator */
    protected $associationHydrator;
    /**
     * {@inheritdoc}
     */
    public function __construct(EntityManager $entityManager, Mapping\ClassMetadata $class)
    {
        parent::__construct($entityManager, $class);
        $this->associationHydrator = new AssociationHydrator($entityManager, $class);
    }

Second step:

    public function findCartForSelectingPayment($id): ?OrderInterface
    {
        /** @var OrderInterface $order */
        $order = $this->createQueryBuilder('o')
            ->andWhere('o.id = :id')
            ->andWhere('o.state = :state')
            ->setParameter('id', $id)
            ->setParameter('state', OrderInterface::STATE_CART)
            ->getQuery()
            ->getOneOrNullResult()
        ;
        $this->associationHydrator->hydrateAssociations($order, [
            'items',
            'items.variant',
            'items.variant.product',
            'items.variant.product.translations',
        ]);
        return $order;
    }