Symfony 4 (Flex) redirect event subscriber in replace of psr-7 middleware

AuthenticatedSubscriber.php

<?php
namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Session\SessionInterface;
use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Class AuthenticatedSubscriber
 *
 * @package App\EventSubscriber
 */
class AuthenticatedSubscriber implements EventSubscriberInterface
{
    /**
     * @var SessionInterface
     */
    protected $session;

    /**
     * NotAuthenticatedSubscriber constructor.
     *
     * @param SessionInterface $session
     */
    public function __construct(SessionInterface $session)
    {
        $this->session = $session;
    }

    /**
     * @param FilterControllerEvent $event
     *
     * @return void
     */
    public function onKernelController(FilterControllerEvent $event)
    {
        $controller = $event->getController();

        //ignore
        if(!is_array($controller)) return;

        if($controller[0] instanceof AuthenticatedSubscriberInterface 
           && $this->session->has('user/auth')) {
            $event->setController(function() {
                return new RedirectResponse('/dashboard');
            });
        }
    }

    /**
     * @return array
     */
    public static function getSubscribedEvents()
    {
        return [
            KernelEvents::CONTROLLER => 'onKernelController',
        ];
    }
}

Essentially I needed to replace my authenticated middleware to check if a user is logged in and not authenticated middleware from a psr-7 project so i could either redirect say from the login form to the dashboard or if not logged in to the login form.

Then all I had to do was implement the interface necessary to the controller itself which is pretty neat. You could probably go as far as to do more specific checks for more complex controllers with multiple actions.

//src/EventSubscriber/AuthenticatedSubscriberInterface.php
interface AuthenticatedSubscriberInterface 
{
}

//src/Controllers/LoginController.php
class LoginController implements AuthenticatedSubscriberInterface
{

}