Hi Apple team, I'm experiencing a persistent issue with writing to UserDefaults from a widget extension on iOS. Here's the situation:
- I've set up an App Group: group.test.blah
- The main app has the correct entitlement and can read/write from UserDefaults(suiteName:) using this group successfully.
- I can read the value written by the app from the widget (e.g., "testFromApp": "hiFromApp").
- The widget extension has the same App Group enabled under Signing & Capabilities.
- The provisioning profile reflects the App Group and the build installs successfully on a real device.
- The suite name is correct and matches across both targets.
- I’ve confirmed via FileManager.default.containerURL(...) that the app group container resolves properly.
When I try to write from the widget extension like this
let sharedDefaults = UserDefaults(suiteName: "group.test.blah")
sharedDefaults?.set("hiFromWidget", forKey: "testFromWidget")
...I get this error in the console:
Couldn't write values for keys (
testFromWidget
) in CFPrefsPlistSource<0x1140d2880> (Domain: group.test.blah, User: kCFPreferencesCurrentUser, ByHost: No, Container: (null), Contents Need Refresh: No): setting preferences outside an application's container requires user-preference-write or file-write-data sandbox access
Questions:
What could still cause the widget extension to lack write access to the app group container, even though it reads just fine?
Are there any internal sandboxing nuances or timing-related issues specific to Live Activity widgets that could explain this?
Is this a known limitation or platform issue?
These limitations are put in on purpose as privacy policies for Widget and LA extensions.
There is no way for an extension to export any of its data to be consumed by another process automatically.
You can use unified logging for post execution debugging by accessing the sysdiagnose from an device, or if you are able to, watch the log output live using the Console app on an attached Mac.
