Check a radio button by default (unmapped ChoiceType field) - forms

Question

I'm trying to have one of the options of a ChoiceType field selected by deafult using Symfony's FormBuilder.
I found a lot of similar questions, but most are about a field mapped to an entity, which is not my case here. The other answers I found involved using the "data" or the "empty_data" attribute, none of which seem to work for me.
Here's my current "add" method (in my FormBuilder):
$builder->add('type2', ChoiceType::class, [
'mapped' => false,
'label' => false,
'choices' => [
"Incoming" => ComEntry::INCOMING,
"Outgoing" => ComEntry::OUTGOING,
],
'expanded' => true,
'empty_data' => 'Incoming',
]);
(I also tried with 'empty_data' => ComEntry::INCOMING,.)
When rendering the form, no radio box is selected, what I would like is to have the first one ("Incoming") selected by default.
Thanks by advance for any reply :-)
EDIT : Here's what I used in the end (instead of 'empty_data' => 'Incoming',), because type2 is a subset of type (type is a sum of bits, type2 is a choice between the INCOMING and the OUTGOING bits).
'choice_attr' => function($choice, $key, $value) use ($options) {
// If the record is being edited and the user selected "Outgoing" at creation, check the "Outgoing" choice.
if($options['data']->getType() & ComEntry::OUTGOING and $choice == ComEntry::OUTGOING)
return ['checked' => 'checked'];
// Else, check the "Incoming" choice.
elseif($choice == ComEntry::INCOMING)
return ['checked' => 'checked'];
else
return [];
},```

Answer 1

You can try using the choice_attr option in its callable form:
This can be an associative array where the keys match the choice keys
and the values are the attributes for each choice, a callable or a
property path.
'choice_attr' => function($choice, $key, $value) use ($options) {
// If no value is set mark INCOMING as checked
if (empty($options['data']->type2) && ComEntry::INCOMING == $value) {
return ['checked' => 'checked'];
}
return [];
},

Answer 2

What you can do is : 'data' => ComEntry::INCOMING instead of the empty_data
The empty_data is useful when the form is submitted.
But this method will work only for creation. For the edition you will have to check if the form has been initialized with data.