learn-healthkit-ios's Introduction

Reading step data from HealthKit, CoreMotion and the app life cycle

Written by: Nguyen Minh Tam

Use case

For general:

App state	Is able to read HealthKit data	Is able to send data	Solution (if exist)
Not running	No	No	Push `Local notification` / `Remote notification`
Inactive	Yes	Yes	Should not (*)
Active	Yes	Yes
Background	Yes	Yes	`Background fetch` with `HeathKit Long-Running Queries` / `CoreMotion` (**)
Suspended	No	No	Change app state to background (***)

(*) App usually stats in the inactive state only briefly as it transition to a different state -> We should not read/send data while in this state.

(**) We can use HeathKit Long-Running Queries just only users don't lock device with password. So we will use CoreMotion to track steps instead.

(***) Change app state to background:

Push notification silently to change app state from suspended to background
With HeathKit, run query in applicationProtectedDataWillBecomeAvailable/ applicationProtectedDataDidBecomeAvailable to check data is encrypted or not.
With CoreMotion, just perform fetch inside application(_:didReceiveRemoteNotification:fetchCompletionHandler:).

In conclusion, we will solve problems by:

App state	Is able to read HealthKit data	Is able to send data	Track steps data
Not running	No	No	Push `Local notification` / `Remote notification`
Inactive	Yes	Yes	Do not track
Active	Yes	Yes	Track normally
Background	Yes	Yes	`Background fetch` with `CoreMotion`
Suspended	No	No	Push `Remote notification` silently

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