Open Radar

 
HKHealthStore allows for an app to subscribe to background delivery of any HKObjectType:

    func enableBackgroundDeliveryForType(_ type: HKObjectType,
                               frequency frequency: HKUpdateFrequency,
                          withCompletion completion: (Bool,
                                                  NSError?) -> Void)

    type - The type of data to observe. This object can be any concrete subclass of the HKObjectType class (any of the classes **HKCharacteristicType** , HKQuantityType, HKCategoryType, HKWorkoutType or HKCorrelationType).

However, it is not currently possible to set up an HKObserverQuery for HKCharacteristicType as the type is restricted to the HKSampleType subclass of HKObjectType:

    init(sampleType sampleType: HKSampleType,
                       predicate predicate: NSPredicate?,
                   updateHandler updateHandler: (HKObserverQuery,
                                          HKObserverQueryCompletionHandler,
                                          NSError?) -> Void)

I humbly ask that the HKObserverQuery API be revised to allow observer queries for HKCharacteristicType.

I recognize that HKCharacteristicType values are not expected to change over time and the current API only allows for an app to ask for the “current” value (-dateOfBirthWithError:). However, it is very common for these values to be empty and if they are later filled in, apps that have access to these values should have a way of being informed. Observer queries seem like the perfect mechanism for the “date of birth was just entered” event.