public function createDataObject($row)
    {
        // remove any composed fields
        $add = [];

        if ($this->_compositeExtraFields) {
            foreach ($this->_compositeExtraFields as $fieldName => $composed) {
                // convert joined extra fields into their composite field types.
                $value = [];

                foreach ($composed as $subField) {
                    if (isset($row[$fieldName . $subField])) {
                        $value[$subField] = $row[$fieldName . $subField];

                        // don't duplicate data in the record
                        unset($row[$fieldName . $subField]);
                    }
                }

                $obj = Injector::inst()->create($this->extraFields[$fieldName], $fieldName);
                $obj->setValue($value, null, false);
                $add[$fieldName] = $obj;
            }
        }

        $dataObject = parent::createDataObject($row);

        foreach ($add as $fieldName => $obj) {
            $dataObject->$fieldName = $obj;
        }

        return $dataObject;
    }