没有数据类如何使用一个表单

// make sure you've imported the Request namespace above the class
use Symfony\Component\HttpFoundation\Request;
// ...
 
public function contactAction(Request $request)
{
    $defaultData = array('message' => 'Type your message here');
    $form = $this->createFormBuilder($defaultData)
        ->add('name', TextType::class)
        ->add('email', EmailType::class)
        ->add('message', TextareaType::class)
        ->add('send', SubmitType::class)
        ->getForm();
 
    $form->handleRequest($request);
 
    if ($form->isValid()) {
        // data is an array with "name", "email", and "message" keys
        $data = $form->getData();
    }
 
    // ... render the form
}

use Symfony\Component\Validator\Constraints\Length;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Form\Extension\Core\Type\TextType;
 
$builder
   ->add('firstName', TextType::class, array(
       'constraints' => new Length(array('min' => 3)),
   ))
   ->add('lastName', TextType::class, array(
       'constraints' => array(
           new NotBlank(),
           new Length(array('min' => 3)),
       ),
   ))
;

new NotBlank(array('groups' => array('create', 'update'))