Validating dynamically loaded choices in Symfony 2

Question

I have a choice field type named *sub_choice* in my form whose choices will be dynamically loaded through AJAX depending on the selected value of the parent choice field, na

Answer 1

To do the trick you need to overwrite the sub_choice field before submitting the form:

public function buildForm(FormBuilderInterface $builder, array $options)
{
    ...

    $builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) {
        $parentChoice = $event->getData();
        $subChoices = $this->getValidChoicesFor($parentChoice);

        $event->getForm()->add('sub_choice', 'choice', [
            'label'   => 'Sub Choice',
            'choices' => $subChoices,
        ]);
    });
}