public function moveSubject(Subject $subject, Category $newCategory)
    {
        $this->om->startFlushSuite();
        $oldCategory = $subject->getCategory();
        $subject->setCategory($newCategory);
        $this->om->persist($subject);
        $this->dispatch(new MoveSubjectEvent($subject, $oldCategory, $newCategory));
        $this->om->endFlushSuite();
    }