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I'm having a strange issue with NSURLSession on the delegate method didFinishDownloadingToURL.

First thing I'm doing is check if the temporary downloaded file exist:

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
                                            didFinishDownloadingToURL:(NSURL *)location
{
    if (![[NSFileManager defaultManager] fileExistsAtPath: [location path]])
    {
        NSLog(@"Error. File not found");
        return; // is giving error when the app is wake up by the system
    }
    ...
}

It works normally when the app is in foreground and download finishes. But when the app is in background and is killed forcedly by the operating system, it returns false.

Does anyone have any idea about what might be happening? I know that there is a time limit for the execution of this delegate method when the app is wake up by the operating system, by it makes no sense for the temporary file to be not there. I can't even copy it to another location... Does it make sense to be because of the size of the file? I'm downloading a file of +-130MB.

Thanks.

Guilherme Gusman
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  • I have the same problem. Filed a bugreport http://openradar.appspot.com/radar?id=4943165404479488 – Biga Oct 21 '15 at 15:44
  • Try opening the URL anyway. The fileExistsAtPath call might be lying to you because of some quirk related to the app sandbox. – dgatwood Oct 28 '15 at 19:38
  • have similar problem. location is pointing to file that does not exists. It doesn't happen often. A bit annoying. I am wondering if this bug is causing bad battery life, because that file will be downloaded again. And if location is wrong again, than downloaded again...etc. – Juraj Antas Dec 31 '15 at 14:10
  • I have the same problem, but using Swift 3 and `FileManager.copyItem(at:to:)` throwing the error "The file “CFNetworkDownload_V2oQ2o.tmp” doesn’t exist." instead of `fileExistsAtPath:` returning `false`. – Nicolas Miari May 16 '17 at 06:13
  • I'm getting this as location /var/mobile/Library/Caches/com.apple.nsurlsessiond/Downloads‌​‌​/com.xxxxxxx/CFNet‌​wo‌​rkDownload_uFBpq‌​p.tm‌​p, but filed doesn't exist there. The only way to currently fix it is to reboot the device and then downloads seem to exist on completion – Zayin Krige Jun 01 '17 at 08:02

2 Answers2

1

I solved the same problem by installing app after uninstall app. It seems that the NSURLSession leaves debris on system when forced shutdown happens while a network session working.

TGT
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  • I am running a Unit Tests target on a framework project (not app) on the Simulator, so not sure how to try your solution. I am **invalidating** the session in both `setUp()` and `tearDown()`... – Nicolas Miari May 16 '17 at 06:15
  • I'm getting this as location /var/mobile/Library/Caches/com.apple.nsurlsessiond/Downloads‌​/com.xxxxxxx/CFNetwo‌​rkDownload_uFBpqp.tm‌​p I'm seeing same behaviour on ios 10.3.2. The only way to currently fix it is to reboot the device – Zayin Krige Jun 01 '17 at 07:59
-2

From the Apple Docs:

(location is..) "A file URL for the temporary file. Because the file is temporary, you must either open the file for reading or move it to a permanent location in your app’s sandbox container directory before returning from this delegate method.

If you choose to open the file for reading, you should do the actual reading in another thread to avoid blocking the delegate queue."

jungledev
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    In the example given, the file is accessed "before returning from this delegate method" — the problem is that it isn't there. The Apple docs are accurate under normal circumstances, but not in the case described above. – Joseph Feb 23 '17 at 23:07