code: public function getFileData($sFieldName) {
          
          if(empty($sFieldName)) {
              return null;
          }
          
          /** @var File $obFile */
          $obFile = $this->$sFieldName;
          if(empty($obFile) || !$obFile instanceof File) {
              return null;
          }
          
          return $this->getFileDataValue($obFile);
      }
docs: Get file data
  @param string $sFieldName
  @return array|null