Doctrine\ODM\CouchDB\Mapping\ClassMetadata::getIdentifierValue PHP Method

    public function getIdentifierValue($document)
    {
        return (string) $this->reflFields[$this->identifier]->getValue($document);
    }

 /**
  * @param object $document
  * @param ClassMetadata $cm
  * @param DocumentManager $dm
  * @return array
  */
 public function generate($document, ClassMetadata $cm, DocumentManager $dm)
 {
     $id = $cm->getIdentifierValue($document);
     if (!$id) {
         throw new \Exception("no id");
     }
     return $id;
 }