Symfony form extrension translator on createView

services.yml

services:
    app.translator_extension:
        class: AppBundle\Form\Extension\TranslatorExtension
        arguments: ['@translator']
        tags:
            - { name: form.type_extension, extended_type: Symfony\Component\Form\Extension\Core\Type\FormType }

TranslatorExtension.php

<?php

namespace KVZBundle\Form\Extension;

use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\Extension\Core\Type\FormType;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormView;
use Symfony\Component\Translation\TranslatorInterface;

class TranslatorExtension extends AbstractTypeExtension
{
    /**
     * @var TranslatorInterface
     */
    private $translator;

    /**
     * TranslatorExtension constructor.
     * @param TranslatorInterface $translator
     */
    public function __construct(TranslatorInterface $translator)
    {
        $this->translator = $translator;
    }


    public function finishView(FormView $view, FormInterface $form, array $options)
    {
        $domain = $form
            ->getConfig()
            ->getOption('translation_domain')
        ;

        $this->translate($view->children, $domain);
    }

    private function translate(&$children, $domain, $locale = 'ru')
    {
        foreach ($children as $name => $child)
        {
            $children[$name]->vars['label'] = $this->translator->trans($child->vars['label'], [], $domain, $locale);
            if(isset($child->vars['children']) && count($child->vars['children']))
            {
                $this->translate($child->vars['children'], $domain);
            }
        }
    }

    /**
     * Returns the name of the type being extended.
     *
     * @return string The name of the type being extended
     */
    public function getExtendedType()
    {
        return FormType::class;
    }
}