protected function _checkFieldType($modelFieldName = null) {
		if (empty($modelFieldName) || !is_string($modelFieldName)) {
			return false;
		}

		if (strpos($modelFieldName, '.') === false) {
			return false;
		}

		list($modelName, $fieldName) = pluginSplit($modelFieldName);
		$schema = $this->_getSchemaForModel($modelName);
		if (($schema === null) || !is_array($schema) || !isset($schema[$fieldName]['type']) ||
			!in_array($schema[$fieldName]['type'], ['text', 'string'])) {
			return false;
		}

		return true;
	}