Better way to run multiple HealthKit sample queries?

Question

I have a scenario where I need to retrieve multiple sets of data from HealthKit -- body temperature, weight, and blood pressure. I need all 3 before I can continue processin

Answer 1

You're going to want to use GCD dispatch groups.

First, set up a global variable for the main thread

var GlobalMainQueue: dispatch_queue_t {
  return dispatch_get_main_queue()
}

Next, create the dispatch group:

let queryGroup = dispatch_group_create()

Right before your queries execute, call:

dispatch_group_enter(queryGroup)

After your query executes, call:

dispatch_group_leave(queryGroup)

Then, handle your completion code:

dispatch_group_notify(queryGroup, GlobalMainQueue) {
  // completion code here
}