Symfony: is it fine to instantiate an entity in the controller?

One of the SOLID principles is Dependency inversion. As I understand it means that I shouldn't instantiate other classes in my code and pass them to the constructor. Is it a violation of this principle when I write this?

UserController extends AbstractController
{
    public function create(Request $request): Response
    {
        $user = new User();
        $form = $this->createForm(RegistrationType::class, $user);

        $form->handleRequest($request);
        if ($form->isSubmitted() && $form->isValid()) {
            $this->entityManager->persist($user);
            $this->entityManager->flush();

            return $this->redirectToRoute('home');
        }

        return $this->render('user/register.html.twig');
    }
}

In the example above I used "new User()".

In my opinion, you aren't violating SOLID principles because of new User() BUT because you're calling the entity manager. I'd rather to use a model layer. In your case, my model is a UserService. Your controller is now depending of it, and if you add new task during this use case, you (or your team) will code it in your controller and you shouldn't and I don't like that.

So I'd rather to use this code:

    #[Route('/register', name: 'app_register')]
    public function register(Request $request, UserService $userService): Response 
    {        
        $user = new User();
        $form = $this->createForm(RegistrationFormType::class, $user);
        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            try {
                $message = $userService->createUser($user);
                $this->addFlash('success', $message);
            } catch (UserServiceException $e) {
                $this->addFlash($e->getLevel(), $e->getReason());
            }

            return $this->redirectToRoute('home');
        }

        return $this->render('registration/register.html.twig', [
            'registrationForm' => $form->createView(),
        ]);

And all the logic steps during user creation are coded in the UserService (persisting, activation email, log for admin, etc.)

My controller only have to know if it works or not. Then it completes the flash message. If it's an exception, it catches a human message (the reason) and forward it to flash message.

If your entity is a bit more complex (let's use a Car with its motor and wheels), you could use a CarModel. It only contains private properties with assertion #[Assert\NotBlank() (like any simple entities) and public getters and setters.

You create your model in your controller new CarModel(), and your model is forwarded by the controller to the CarService as soon as the form is submitted and valid. CarService will create the complex Car entity, the Motor entity, the four Wheels entities from the Model, persist them.

To summarize, my controller :

• directly creates the simple entities, or a model for complex use case with a new MyEntity() or `new MyModel();
• uses the request to create form and complete entities ;
• uses the request to know if the form has been submitted is valid ;
• calls the model layer (UserService) to execute the use case ;
• completes the flash messages based on the result,
• completes and render the view or redirects the user.