protected function _getSchema($model = null) {
		$result = null;
		if (empty($model)) {
			return $result;
		}

		$modelObj = ClassRegistry::init($model, true);
		if ($modelObj === false) {
			return $result;
		}

		$result = $modelObj->schema();
		if (empty($modelObj->virtualFields)) {
			return $result;
		}

		foreach ($modelObj->virtualFields as $virtualFieldName => $virtualFieldVal) {
			$result[$virtualFieldName] = ['type' => 'string'];
		}

		return $result;
	}