You must request open access in order to access shared NSUserDefaults. It’s stated directly in the App Extension Programming guide: By default, a keyboard has no network access and cannot share a container with its containing app. To enable these things, set the value of the RequestsOpenAccess Boolean key in the Info.plist file to YES. … Read more
I faced the same issue, and in my case my apple id did not have the permission to add the “App Group”. If your account’s type is “Member”, not “Agent”, then you need your Agent/Admin who has the main development account to add the “App Group” for you.
You cannot use UserDefaults.standard to share data between a host app and its app extension. You instead have to create a shared container with UserDefaults(suiteName:) to share data. Even though an app extension bundle is nested within its containing app’s bundle, the running app extension and containing app have no direct access to each other’s … Read more
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 … Read more