Dependency Injection not Occurring in Symfony 2.8 - php

Question

I have a controller, ApiBundle\Controller\UserController, and it has the following contents:
<?php
namespace ApiBundle\Controller;
use Doctrine\ORM\EntityManager;
use FOS\RestBundle\Controller\Annotations\Route;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Method;
use Symfony\Component\HttpFoundation\Request;
use AppBundle\Entity\User;
use ApiBundle\Form\RegisterType;
use ApiBundle\Utility\ApiUtility;
class UserController extends ApiController
{
/**
* #var EntityManager $em
*/
private $em;
/**
* UserController constructor.
* #param EntityManager $entityManager
*/
function __construct(EntityManager $em)
{
$this->em = $em;
}
/**
* #Route("register")
* #Method({"POST"})
* #return \Symfony\Component\HttpFoundation\Response
* #param Request $request
*/
public function registerUser(Request $request)
{
$data = ApiUtility::getContentAsArray($request);
$user = new User();
$form = $this->createForm(new RegisterType(), $user);
$form->submit($data);
if($form->isValid()) {
$user->setUsername($request->get('email'));
$this->em->persist($user);
$this->em->flush();
}else{
return ApiUtility::returnResponse($form->getErrors());
}
}
}
It extends API Controller, seen here:
<?php
namespace ApiBundle\Controller;
use FOS\RestBundle\Controller\FOSRestController;
class ApiController extends FOSRestController
{
}
And it has the following services:
services:
api.controller.user:
class: ApiBundle\Controller\UserController
public: false
parent: api.controller
arguments: ["#doctrine.orm.entity_manager"]
api.controller:
class: ApiBundle\Controller\ApiController
calls:
- [setContainer, ['#service_container']]
No matter what I do, I can't get the container to inject. Right now, when I just try to get doctrine into the container through the constructor, I get Type error: Too few arguments to function ApiBundle\Controller\UserController::__construct(), 0 passed in app/cache/dev/classes.php on line 2230 and exactly 1 expected, if I switch it back to $this->container->get('doctrine.orm.entity_manager') or getEntityManager, I get container is null. How can I fix this?