didReceiveRemoteNotification中的UIBackgroundFetchResult

Question

在didReceiveRemoteNotification调用中，UIBackgroundFetchResult在completionHandler中的含义是什么？那就是 - SDK使用UIBackgroundFetchResult的目的是什么？

 - (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler 

具体来说，无论我在收到推送通知时是否提取了新数据，如果我返回以下内容会发生什么？

UIBackgroundFetchResult fetchResults = UIBackgroundFetchResultNewData;
if (completionHandler) {
    completionHandler(fetchResults);
}