UIDatePicker bug? UIControlEventValueChanged after

Question

I've run into a weird effect that sure looks like a bug in iOS7 -- but often in the past, when I have thought I found a bug in Apple's APIs, it has turned out to be my own misunderstanding.

I have a UIDatePicker with datePickerMode = UIDatePickerModeCountDownTimer and minuteInterval = 5. I initialize the duration to 1 hour, and present it to the user, where it appears as a two-column picker with hours and minutes. (So far so good.)

The user is thinking "20 minutes," and so scrolls the Hour column to 0. At this point the picker reads 0 hours and 0 minutes, and iOS7 is not cool with that, so it automatically scrolls the minute wheel to 5. My UIControlEventValueChanged handler gets invoked, and the countDownDuration reads 5 minutes. (Still good.)

Now the user grabs the minute wheel and drags it to 20. AND... my UIControlEventValueChanged handler does not get called. (Bad.)

If I have some other event in the UI check the date picker at this point, I do see the countDownDuration is set to 20. But I had no way of knowing that the user changed it, at the moment it was changed. This is very repeatable: it always happens on the first change AFTER the picker refuses to be set to 0 (advancing itself to 5 minutes).

Note that this is in iOS7; it does not occur in iOS6 (perhaps because the picker there is perfectly content to be set to 0 minutes).

So... am I missing something here? Or is this a genuine bug in iOS7? And in the latter case, does anybody know a work-around better than having some timer periodically check the current interval?

Answer 1

For Swift 3:

DispatchQueue.main.async(execute: {
    yourPicker.countDownDuration = TimeInterval() 
})