Re: Various iOS apps log out randomly, lose all data & settings

This issue exists for about a year now (it seems that this bug was introduced in iOS 9.3.1 and is still present in iOS 10.2).

The problem seems to be that after an App is launched and tries to load its settings from NSUserDefaults, it does not get any data. It looks like NSUserDefaults sometimes "forgets" to load its data from the file system. If you manage to kill the App before it tries to store new data in NSUserDefaults and the restart the App, chances are good that this time NSUSerDefaults does load the data correctly and the App can get all its settings again. But as soon as the App stores anything in NSUserDefaults, all old data is overwritten and lost forever.

But killing an App before it can store anything in NSUserDefaults is usually only possible for your own Apps when running them in the debugger.

There are a lot of threads here in the developer forums related to this topic. We all hope that Apple will someday find and fix this annoying bug. Even though with some luck the issue won't show up very often, it is nevertheless very annoying. Please send bug reports to Apple, so Apple learns that this is serious.

Here are a few other related threads:

https://forums.developer.apple.com/thread/44264

https://forums.developer.apple.com/thread/44685

https://forums.developer.apple.com/thread/61287

https://forums.developer.apple.com/thread/28030

Hm, I'm currently furiously looking for the reason users in our app is being logged out. I use NSUserDefaults with encryption to store the authentication token. For some reason, after our last update, users are logged out en masse. We have barely changed the code at all. And surely nothing considering the saving of the token. My initial fear was that [[UIDevice currentDevice]identifierForVendor] had changed after update. I've found bugs on that reported previously.

Hi, I have the same issue since I started developing for/on the iPhone with a second Mac and a second Apple ID...

I have encountered this in development. I found that I can access the keys that should be there by inserting a random value into NSUserDefaults and checking again.

    BOOL seen = [[NSUserDefaults sharedUserDefaults] objectForKey:MY_KEY] != nil;

    if (!seen) {

        // are you sure? try again...

        [[NSUserDefaults sharedUserDefaults] setObject:[NSUUID UUID].UUIDString

                                                 forKey:@"TEMP_KEY"];

        seen = [[NSUserDefaults sharedUserDefaults] objectForKey:MY_KEY] != nil;

    }

    return seen;