xcode - Failed to read values in CFPrefsPlistSource iOS 10

Question

I've updated my Xcode 8 to beta 2 today and I'm trying to share data between App and Today Extension. I'm facing with this log warning:

2016-07-08 18:00:24.732472 ProjetctX[941:42801] [User Defaults] Failed to read values in CFPrefsPlistSource<0x1700f1280> (Domain: group.x.p.t.o, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null)): Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd

Anyone can help me?

Answer 1

This is actually a spurious warning that was introduced in iOS 10 and macOS 10.12:

NSUserDefaults tip: in the current OSs there's a logged error "…with a container is only allowed for System Containers…".

This is spurious.

Trying to catch a particular failure mode, caught a normal operation case at the same time.

My successor on UserDefaults also has not figured out a way to make this less alarming without making the symptomatic case impossible to debug :/

https://twitter.com/Catfish_Man/status/784460565972332544 [thread]

The advice of prepending your team ID will silence the warning, but will also create a new empty user defaults. This will result in any previously stored data being unreadable.

For the time being, the solution is just to ignore it.

Also, Apple staff member CFM on the forums:

The logged message is spurious unless you're doing very specific things that I don't think are possible without using private functions (it was added to catch misuse of those functions, but unfortunately also caught a normal usage case).