How to map two entities in the one Symfony Form - forms

Question

The problem I am having now is related to entities and forms in Symfony2.
While creating the form that refers to one entity I can simply wire it by saying:
$user = new User();
$form->createForm(new UserType(), $user);
...
$manager->persist($user);
$manager->flush();
And that is working fine. But the problem raises when I have more complex form that is built based on other forms, e.g.
So, let's imagine I have a form called RegistrationType that contains two other forms called UserType wired to User entity and ProfileType wired to Profile entity.
Now, how can I handle that in the controller? I mean, I cannot do something like:
$user = new User();
$profile = new Profile();
$form->createForm(new RegisterType(), $user, $profile);
OR
$form->createForm(new RegisterType(), [$user, $profile]);
...
$manager->persist($user);
$manager->flush();
$profile->setUserId($user->getId());
$manager->persist($profile);
$manager->flush();
If I pass only $user, like so
$form->createForm(new RegisterType(), $user);
Symfony will complain that there are properties that are not mapped, of course I can set them to 'mapped' => false but then I have to set them later on manually.
What's the best way to handle this?
Thanks in advance!

Answer 1

Create UserType, ProfileType and RegistrationType forms. RegistrationType should add UserType and ProfileType as its children. Create Registration DTO and set it as data_class for RegistrationType. Then you can write something like
$user = new User();
$profile = new Profile();
$form->createForm(new RegistrationType(),
new Registration($user, $profile));