Note as of Symfony 3.3 EntityManager is depreciated. Use EntityManagerInterface instead.
namespace AppBundle\Service;
use Doctrine\ORM\EntityManagerInterface;
class Someclass {
protected $em;
public function __construct(EntityManagerInterface $entityManager)
{
$this->em = $entityManager;
}
public function somefunction() {
$em = $this->em;
...
}
}