I'm writing my own fitness app that I hope to bridge the void between the Fitbit app and Apple Health (I finally ditched my Blaze for an Apple Watch). So far I am able to retrieve the workouts for the last 7 days but I want to display a heart rate graph (like Fitbit does) for the workout when you click to view it. Does the workout contain the heart rate samples recorded during the workout or do I need to query the heart rate for start and end time matching the workout separately? I've played about a bit and tried to find the answer in the documentation but I'm finding it a bit difficult to understand so sorry if I've missed something obvious!
The Workout app on Apple Watch does not associate heart rate samples with its HKWorkout instances, so querying for heart rate samples using +[HKQuery predicateForObjectsFromWorkout:] will not return any results. Instead, you should query for heart rate samples using a date range predicate spanning the duration of the workout.