Symfony form builder Add instance of \DateTime - php

Question

I'm trying since some of hour to add a \DateTime validation in a form builder
The Customer entity (Sample):
class Customer
{
/**
* #Assert\NotBlank
* #Assert\Type("\DateTime")
* #MongoDB\Field(type="date")
*/
private $birthDate;
/**
* #return \DateTime
*/
public function getBirthDate() : ? \DateTime
{
return $this->birthDate;
}
/**
* #param int $birthDate
*/
public function setBirthDate(int $birthDate) : self
{
$this->birthDate = (new \DateTime())->setTimeStamp($birthDate);
return $this;
}
}
The form builder is like this (Sample):
class CustomerType extends AbstractType
{
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder->add('birthDate', DateTimeType::class, ['data_class' => \DateTime::class]);
}
/**
* #param OptionsResolver $resolver
*/
public function configureOptions(OptionsResolver $resolver)
{
$resolver->setDefaults([
'data_class' => Customer::class,
'csrf_protection' => false
]);
}
}
When I want to submit the form, I received always a error:
The form's view data is expected to be an instance of class DateTime, but is a(n) array. You can avoid this error by setting the \"data_class\" option to null or by adding a view transformer that transforms a(n) array to an instance of DateTime.
The user is sending the good parameter:
"customer": {
"birthDate": 30459425029458,
}
I tryed to follow this solution without success
Symfony2.1 form date field: Argument 1 passed to ... must be an instance of DateTime
And the view transformer return a null value
$builder->get('birthDate')
->addModelTransformer(new CallbackTransformer(
function ($tagsAsArray) {
// transform the array to a string
return implode(', ', $tagsAsArray);
},
function ($tagsAsString) {
// transform the string back to an array
return explode(', ', $tagsAsString);
}
))
;
I tried to switch data-class option to null but the form send me a no valid value error.
How can I validate a instance of \DateTime in formBuilder?
Thanks in advance
EDIT:
Temporary bad solution:
if(isset($params['customer']['birthDate'])) {
$customer->setBirthDate($params['customer']['birthDate']);
} else {
$this->error = ['message' => 'birthDate missing'];
return false;
}