symfony 4 - BaseFixture

<?php

namespace App\DataFixtures;

use Doctrine\Bundle\FixturesBundle\Fixture;
use Doctrine\Common\Persistence\ObjectManager;
use Faker\Factory;
use Faker\Generator;

abstract class BaseFixture extends Fixture
{
    /** @var ObjectManager */
    private $manager;
    
    /** @var Generator */
    protected $faker;
    
    private $referencesIndex = [];
    
    abstract protected function loadData(ObjectManager $manager);
    
    public function load(ObjectManager $manager)
    {
        $this->manager = $manager;
        $this->faker = Factory::create();
        $this->loadData($manager);
    }
    
    /**
     * Create many objects at once:
     *
     *      $this->createMany(10, function(int $i) {
     *          $user = new User();
     *          $user->setFirstName('Ryan');
     *
     *           return $user;
     *      });
     *
     * @param int      $count
     * @param string   $groupName Tag these created objects with this group name,
     *                            and use this later with getRandomReference(s)
     *                            to fetch only from this specific group.
     * @param callable $factory
     */
    protected function createMany(int $count, string $groupName, callable $factory)
    {
        for ($i = 0; $i < $count; $i++) {
            $entity = $factory($i);
            if (null === $entity) {
                throw new \LogicException('Did you forget to return the entity object from your callback to BaseFixture::createMany()?');
            }
            $this->manager->persist($entity);
            // store for usage later as groupName_#COUNT#
            $this->addReference(sprintf('%s_%d', $groupName, $i), $entity);
        }
    }
    
    protected function getRandomReference(string $groupName) {
        if (!isset($this->referencesIndex[$groupName])) {
            $this->referencesIndex[$groupName] = [];
            foreach ($this->referenceRepository->getReferences() as $key => $ref) {
                if (strpos($key, $groupName.'_') === 0) {
                    $this->referencesIndex[$groupName][] = $key;
                }
            }
        }
        if (empty($this->referencesIndex[$groupName])) {
            throw new \InvalidArgumentException(sprintf('Did not find any references saved with the group name "%s"', $groupName));
        }
        $randomReferenceKey = $this->faker->randomElement($this->referencesIndex[$groupName]);
        return $this->getReference($randomReferenceKey);
    }
    
    protected function getRandomReferences(string $className, int $count)
    {
        $references = [];
        while (count($references) < $count) {
            $references[] = $this->getRandomReference($className);
        }
        return $references;
    }
}