Symfony4 Forms - How do you conditionally disable a form field? - forms

Question

So what is the best way to have a form render effectively the same form over and over again, with conditionally disabled fields based on the Entity's property values?
I have an Invoice Entity and need a form for creating the invoice, and also the same form with various fields disabled at various stages of the invoicing process (generated, sent, paid etc).
I think the simplest answer is to disable them dynamically in the twig template via form_row options but surely this will affect server side validation of the form as it is not aware the field has been disabled?
What is the best way to disbale a field based on a value in the database?
EDIT 1:
Changed question from Dynamically disable a field in the twig template or seperate class for each form? to Symfony4 Forms - How do you conditionally disable a form field?

Answer 1

Thanks to #Cerad. The answer is in fact Form Events
In the form type (App\Form\InvoicesType for me), add a method call to the end of the builder:
public function buildForm(FormBuilderInterface $builder, array $options)
{
$plus_thirty_days = new \DateTime('+28 days');
$builder
->add('client', EntityType::class, array(
'class' => Clients::class,
'choice_label' => 'name',
'disabled' => false,
) )
// the event that will handle the conditional field
->addEventListener(
FormEvents::PRE_SET_DATA,
array($this, 'onPreSetData')
);;
}
and then in the same class, create a public method named the same as the string in the array (onPreSetData for this example):
public function onPreSetData(FormEvent $event)
{
// get the form
$form = $event->getForm();
// get the data if 'reviewing' the information
/**
* #var Invoices
*/
$data = $event->getData();
// disable field if it has been populated with a client already
if ( $data->getClient() instanceof Clients )
$form->add('client', EntityType::class, array(
'class' => Clients::class,
'choice_label' => 'name',
'disabled' => true,
) );
}
From here you can update the field to be any valid FormType and specify any valid options as you would a normal form element in the From Builder and it will replace the previous one, laving it in the same original position in the form.