Symfony form builder: How to iterate/render dynamic amount of text fields in twig? (Sylius - exta checkout step) - symfony

Question

I added an extra checkout step to the Sylius checkout procedure and I am trying to add 1 text field per instance of an ordered item. Thus having put 3x itemA and 1x itemB in cart should spawn 4 text fields.
I have this code so far in the form builder (based on code from here: https://sf.khepin.com/2011/08/basic-usage-of-the-symfony2-collectiontype-form-field/)
$builder->add('myCollection', CollectionType::class, $formOptions);
$totalCounter = 0;
/** #var OrderItem $item */
foreach($order->getItems() as $item) {
for($itemCounter = 0 ; $itemCounter < $item->getQuantity(); $itemCounter++ ) {
$totalCounter++;
$builder->get('myCollection')->add('item_' . $totalCounter, TextType::class, $formOptions);
}
}
First Question: Is this the right approach for the form builder for my particular scenario, and secondly: If yes, how do I read from this in the twig template?
form.children.myCollection does exist but does not seem to contain these children, so that I could use them with the form_row function. What I would have expected is something like this:
{% set totalCounter = 0 %}
{% for item in order.items %}
{% for itemCounter in 1..item.quantity %}
{% set totalCounter = totalCounter + 1 %}
{{ form_row(form.children.myCollection['item_' ~ totalCounter ]) }}
{% endfor %}
{% endfor %}
Any idea how to do this? Thanks for any hint in advance!

Answer 1

Just saw my exact case is described in the beginning of the documentation of CollectionType https://symfony.com/doc/current/reference/forms/types/collection.html
The form builder part..
$builder->add('emails', CollectionType::class, [
// each entry in the array will be an "email" field
'entry_type' => EmailType::class,
// these options are passed to each "email" type
'entry_options' => [
'attr' => ['class' => 'email-box'],
],
]);
..and the twig part:
{{ form_label(form.emails) }}
{{ form_errors(form.emails) }}
<ul>
{% for emailField in form.emails %}
<li>
{{ form_errors(emailField) }}
{{ form_widget(emailField) }}
</li>
{% endfor %}