（Symfony 4表单类型）如何基于 <select>价值形式？

Question

Here is my form type class. So the < select> field I am talking about is the 'numSubscriptionTiers':

class UserProfileType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('numSubscriptionTiers', ChoiceType::class, [
                'choices' => [
                    '1' => 1,
                    '2' => 2,
                    '3' => 3
                ]
            ])
            ->add('subscriptionTier1', UserSubscriptionTierType::class, [
                'required' => false,
                'entry_type' => UserSubscriptionTierType::class
            ])
            ->add('subscriptionTier2', UserSubscriptionTierType::class, [
                'required' => false,
                'entry_type' => UserSubscriptionTierType::class
            ])
            ->add('subscriptionTier3', UserSubscriptionTierType::class, [
                'required' => false,
                'entry_type' => UserSubscriptionTierType::class
            ])

If the user selects 1, then only make the subscriptionTier1 subform required, if the user selects 2, then only make the subscriptionTier1 and subscriptionTier2 subforms required, and so on...

I know there are form events like PRE_SET_DATA, POST_SUBMIT, etc... but can you add something similar to a JavaScript event from within the form type class? Like some kind of onChange event to the numSubscriptionTiers select, and set the corresponding subforms' required attribute to true/false?

I have already gone here: https://symfony.com/doc/current/form/dynamic_form_modification.html#how-to-dynamically-generate-forms-based-on-user-data and it only gives an example of how to dynamically populate a choice list, not add a change event after it's options are specified.

Answer 1

Use the PRE_SUBMIT event to modify the form dynamically to set the backend validation on your form elements.

Eg, if the sent value of the numSubscriptionTiers is 2 , then remove children subscriptionTier1 and subscriptionTier2 and add them again, but this time with additional NotBlank constraint:

// add imports

public function buildForm(FormBuilderInterface $builder, array $options)
{
    // skipped for brevity
    $builder->addEventListener(FormEvents::PRE_SUBMIT, [$this, 'conditional']);
}

public function conditional(FormEvent $event)
{
    $form = $event->getForm();
    $data = $event->getData();

    // make sure tierCount is between 1-3
    $tierCount = min(3, max(1, (int) $data['numSubscriptionTiers'] ?? 0));

    for ($i = 1; $i <= $tierCount; $i++) {
        $childName = sprintf('subscriptionTier%d', $i);

        $form
            ->remove($childName)
            ->add($childName, UserSubscriptionTierType::class, [
                'required' => false,
                'entry_type' => UserSubscriptionTierType::class,
                'constraints' => new NotBlank(),
            ]);
    }
}

I'm afraid the HTML5 required attribute has to be added dynamically using JavaScript, because PHP won't handle that on the client side. Well you could modify the required property of the dynamically readded field subscriptionTier1 , but think what would happen if the user would change the numSubscriptionTiers to 2 . It would be impossible to submit the form, because of the required property on the subscriptionTier1 element. Thus only JavaScript is a solution to that.