private function copyPlayground(Playground $source_playground, Playground $target_playground)
 {
     $em = $this->getDoctrine()->getManager();
     /* @var $attr PlaygroundAttribute */
     foreach ($source_playground->getPlaygroundAttributes() as $attr) {
         if ($this->get('logic')->getPlaygroundAttribute($target_playground->getId(), $attr->getDate(), $attr->getStart()) == null) {
             $target_attr = new PlaygroundAttribute();
             $target_attr->setPlayground($target_playground);
             $target_attr->setTimeslot($attr->getTimeslot());
             $target_attr->setDate($attr->getDate());
             $target_attr->setStart($attr->getStart());
             $target_attr->setEnd($attr->getEnd());
             $target_attr->setFinals($attr->getFinals());
             $em->persist($target_attr);
         }
     }
     $em->flush();
 }