private function getFileDownloadSrc($file, $relation)
    {
        $id = is_null($relation) ? $this->id : $this->$relation;
        return route('download.document',['id' => $id]);
    }
private function getFileDownloadSrc($file, $relation)
    {
        $id = is_null($relation) ? $this->id : $this->$relation;
        return route('download.document',['id' => $id]);
    }
private function getFileDownloadSrc ( $ file , $ relation ) { $ id = is_null ( $ relation ) ? $ this -> id : $ this -> $ relation ; return route ( 'download.document' , [ 'id' => $ id ] ) ; }
get the file download src

@param string $file
@param string|null $relation
@return string
get the file download src