IOS HealthKit today step count is always 0 (but end days are ok)

In our application, we request HealthKit to keep track of 7 days counters, summed daily, with a midnight point. So the range is D-6 midnight to midnight tomorrow (as we wanted the steps today so far).

This is what it works and we can always get the latest 6 days of data, except that it is always 0 today.

But the weird part is that if we open the default iHealth app that ships with iOS 8.0, it calculates the health data and shows today's steps in a graph. And then if we reopen our app and reload the chart data, today the steps there miraculously match what "iHealth" shows.

So the iPhone only generates daily counts automatically at midnight and caches it or something? Is there a separate challenge we need to make in order to calculate today's data or something before any health indicators are obtained?

Here's the function we're calling to get the data:

func queryDailyStats(metric: NSString!, handler: ([NSDate: Int] -> Void)!) {
    let quantityType = HKObjectType.quantityTypeForIdentifier(metric)
    let calendar = NSCalendar.currentCalendar()
    let now = NSDate()
    let preservedComponents: NSCalendarUnit = (.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay)
    let midnight: NSDate! = calendar.dateFromComponents(calendar.components(preservedComponents, fromDate:now))
    let dailyInterval = NSDateComponents()
    dailyInterval.day = 1

    let tomorrow = calendar.dateByAddingUnit(.MonthCalendarUnit, value: 1, toDate: midnight, options: nil)
    let oneMonthAgo = calendar.dateByAddingUnit(.MonthCalendarUnit, value: -1, toDate: midnight, options: nil)
    let oneWeekAgo = calendar.dateByAddingUnit(.DayCalendarUnit, value: -6, toDate: midnight, options: nil) // only need to start from 6 days back

    // need tomorrow midnight as end date to get all of today data
    let predicate = HKQuery.predicateForSamplesWithStartDate(oneWeekAgo, endDate: tomorrow, options: .None)

    let query = HKStatisticsCollectionQuery(
        quantityType: quantityType,
        quantitySamplePredicate: predicate,
        options: .CumulativeSum,
        anchorDate: midnight,
        intervalComponents: dailyInterval
    )

    query.initialResultsHandler = { query, results, error -> Void in
        var data:[NSDate: Int] = [:]
        if error != nil {
            println(error)
        } else {
            results.enumerateStatisticsFromDate(oneWeekAgo, toDate: midnight) { statistics, stop in
                if let quantity = statistics.sumQuantity() {
                    let date = statistics.startDate
                    let value = Int(quantity.doubleValueForUnit(HKUnit.countUnit()))

                    data[date] = value
                }
            }
        }

        handler(data)
    }

    self.healthKitStore.executeQuery(query)
}