Symfony and JMS Serialier, Listener to add extra fields

ResponseSerializationSubscriber.php

<?php
/**
 * Created by PhpStorm.
 * User: bhaktaraz
 * Date: 9/11/19
 * Time: 11:33 AM
 */

namespace App\Serializer;

use App\Entity\User;
use App\Entity\AccessCode;
use Doctrine\ORM\EntityManagerInterface;
use JMS\Serializer\EventDispatcher\ObjectEvent;
use JMS\Serializer\Metadata\StaticPropertyMetadata;
use JMS\Serializer\EventDispatcher\EventSubscriberInterface;

class ResponseSerializationSubscriber implements EventSubscriberInterface
{
    private $em;

    public function __construct(EntityManagerInterface $em)
    {
        $this->em = $em;
    }

    public static function getSubscribedEvents()
    {
        return [
            ['event' => 'serializer.post_serialize', 'method' => 'onPostSerialize'],
        ];
    }
    
    public function onPostSerialize(ObjectEvent $event)
    {
        $object = $event->getObject();

        if($object instanceof User) {
            $code = $this->em->getRepository(AccessCode::class)->findOneBy(['code' => $object->getClinicCode()]);
            $clinic = $code->getClinic();

            $visitor = $event->getVisitor();

            $visitor->visitProperty(new StaticPropertyMetadata(User::class, 'clinic_name', $clinic->getName()), $clinic->getName());
        }
    }
}