Save/Delete to HealthKit With WatchKit and Widget (Today Extension)? - ios

Question

Here is a question that I know has an answer since I see apps that do this functionality. I have tried (writing directly, using background fetch) but nothing works. I found an app currently on the app store with the functionality that I am looking for. With Background Fetch set to OFF and main app NOT running in background. I go to the Widget and add an item. I open HealthKit and I see the data there as expected.
I would like to do the same for my app. I would like my today extension (widget) and/or WatchKit extension to write to the HealthKit store even when app is not running in background.
Like I said I have tested an app that does this functionality even though in Apple documentation it says this:
The HealthKit store can only be accessed by an authorized app. You
cannot access HealthKit from extensions (like the Today view) or from
a WatchKit app.
Because the HealthKit store is encrypted, your app cannot read data
from the store when the phone is locked. This means your app may not
be able to access the store when it is launched in the background.
However, apps can still write data to the store, even when the phone
is locked. The store temporarily caches the data and saves it to the
encrypted store as soon as the phone is unlocked.
Any answers or insights are appreciated. Thanks everybody.

Answer 1

The Health Data Store is indeed encrypted while the device is locked. Locked is defined as requiring a passcode on the device and the screen was turned off (so a passcode or touch id is required before you can get back to the main screen). While the store is encrypted it is not possible to read any data from it, no matter if the app is running in the background or not. Even setting up observer queries while the app is running will not allow it to continue to be read from. I imagine this level of protection is done simply using the Data Protection capability with the NSFileProtectionComplete option.
What HealthKit functionality have you observed in this other app? If it was displaying step and distance data, then they are likely getting this data directly from the pedometer (CMPedometer), which is not restricted when the device is locked.

Answer 2

Lehn0058's comment about authorization was correct. I had to request authorization explicitly from the WatchKit and Today Extension even though authorization was already given in the app. Afterwards both are able to write to the Health Store. The comment from Apple above only has to do with Reading from the Health Store and NOT writing to the Health Store. Here is some sample code for anybody else who gets in to the same problem. Thanks again.
In WatchKit InterfaceController.m
- (void)awakeWithContext:(id)context {
[super awakeWithContext:context];
// Configure interface objects here.
[[HealthKitManager sharedManager] requestHealthKitAccess];
}
In Today Extension TodayViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
[[HealthKitManager sharedManager] requestHealthKitAccess];
}