public function reverseTransform($tagString)
 {
     $tagCollection = new ArrayCollection();
     if (empty($tagString)) {
         return $tagCollection;
     }
     $slugify = new Slugify();
     foreach (explode(',', $tagString) as $tag) {
         $tag = trim($tag);
         $tagSlugged = $slugify->slugify($tag);
         $tagEntity = $this->em->getRepository('AppBundle:Tag')->findOneBy(array('tag' => $tagSlugged));
         if (!$tagEntity instanceof Tag) {
             $tagEntity = new Tag();
             $tagEntity->setTag($tagSlugged);
         }
         $tagCollection->add($tagEntity);
     }
     return $tagCollection;
 }