Yhyjyk

In a custom module, I have a form that is triggered by an option in a menu.

I'd want this form to be redirected automatically (without action of the user) to a certain node (/node/2) when the user is not authenticated.

In the public function buildForm(array $form, FormStateInterface $form_state) {, I know how to not display the fields of the form for the anonymous user:

$oCurrentUser = Drupal::currentUser();
if ($oCurrentUser->isAnonymous()) 
 else 

some fields... 

$form['submit'] = [
 '#type' => 'submit',
 '#value' => $this->t('Submit'),
];
return $form;

I guess that redirection might be done with $form_state->setRedirect('entity.node.canonical', ['node' => 2]);
but I don't know how to make it work...

Any idea?

In buildForm() you can return a redirect response the same way as in a controller:

 public function buildForm(array $form, FormStateInterface $form_state) 
 if ($this->currentUser()->isAnonymous()) 
 return $this->redirect('entity.node.canonical', ['node' => 2]);
 

 // build $form for authenticated users

 return $form;
 

Use $form_state->setRedirect() if you want to redirect in a form submit handler.

The class implementing FormInterface is allowed to return an instance of a class extending the Response class, despite FormInterface::buildForm() not documenting it. See what a comment in the FormBuilder::retrieveForm() code says.

Exceptions should not be used for code flow control. However, the Form API currently allows any form builder functions to return a response.

This means that code similar to the following one would actually work.

public function buildForm(array $form, FormStateInterface $form_state) 
 // Verify the currently logged in user is an anonymous user and redirect.
 if ($this->currentUser()->isAnonymous()) 
 return $this->redirect('entity.node.canonical', ['node' => 2]);
 

Although, since Do not allow form builder functions to return Response objects is open for Drupal 8.8.x, that code could not work anymore, in future.

A module that works also after the change described in that issue is implemented would:

• Associate a controller to the route, not a form builder


• 
  

  In the controller method associated with the route, redirect the anonymous users to the node page, or render the form for authenticated users

  
  
  

  class RedirectOrFormController extends ControllerBase 
   public function showForm() 
   if ($this->currentUser()->isAnonymous()) 
   return $this->redirect('entity.node.canonical', ['node' => 2]);
   
  
   return $this->formBuilder()->getForm('Drupal\locale\Form\TranslateEditForm');
   
  
  

  
  

Replace 'Drupal\locale\Form\TranslateEditForm' with the fully qualified name of the form builder.

yes, you are right. you can redirect to the node using the code that you have mentioned. There is another way to set the redirection check the below code.

use the name space :

 
use SymfonyComponentHttpFoundationRedirectResponse;
$response = new RedirectResponse(node url);
$response->send();
exit(0);

I don't know what you are trying to achieve hope this code may help you.