how to make the selected offer checked?

controller.php

        $data = [
            'offer' => new OfferForCustomer($ticket->getCustomer(), $ticket->getOffer(), 0, 0, 0),
        ];
        $form = $this->createForm('season_ticket', $data, [

formtype.php

        $builder
            ->add('offer', 'choice', [
                'data_class' => 'App\Domain\Model\OfferForCustomer', // i have to specify it or it will only accept scalar during setData
                'constraints' => [new Assert\NotBlank],
                'choices' => $this->offers->getAvailableOffers($options['customer'], $options['seller']), // array of VOs
                'expanded' => true,
                'choices_as_values' => true,
                'choice_label' => 'name',
                'choice_value' => 'id',
            ])
        ;