nextTriggerDate() doesn't return the 'expected' value, is there another way to obtain the next fire date of a repeating Local Notification?

Question

In my application I allow users to schedule repeating Local Notifications. The issue that I have though (any many others based on looking around) is that nextTriggerDate() alway

Answer 1

Confirmed. I ran this code:

let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 120, repeats: true)
print("scheduling at", Date())
DispatchQueue.main.asyncAfter(deadline: .now()+15) {
    print("checking at", Date())
    UNUserNotificationCenter.current().getPendingNotificationRequests {
        arr in let arr = arr
        if let req = arr[0].trigger as? UNTimeIntervalNotificationTrigger {
            let fd = req.nextTriggerDate()
            print("trigger date", fd as Any)
        }
    }
}
// ... proceed to configure and schedule the notification

I also configured my user notification center delegate to receive the notification in the foreground and print the time.

Here's what I saw in the console:

scheduling at 2018-08-01 03:40:36 +0000
checking at 2018-08-01 03:40:51 +0000
trigger date Optional(2018-08-01 03:42:51 +0000)
received notification while active 2018-08-01 03:42:36 +0000

So the trigger date was reported as 2 minutes from when I checked, but the notification actually fired 2 minutes from when I scheduled it.

I'd describe that as a bug!

The one disagreement I'd have with your original question is that I get exactly the same result for a non-repeating UNTimeIntervalNotificationTrigger:

scheduling at 2018-08-01 03:45:50 +0000
checking at 2018-08-01 03:46:06 +0000
trigger date Optional(2018-08-01 03:48:06 +0000)
received notification while active 2018-08-01 03:47:50 +0000

A UNTimeIntervalNotificationTrigger also has a timeInterval property, but even that does us no good unless we know when the notification was originally scheduled — and a UNNotificationRequest provides no way to find that out.

(Just to be certain, I postponed my checking until the repeating notification had fired a couple of times, but the result was the same: nextTriggerDate is clearly adding the timeInterval to now rather than reporting the time at which the notification will next fire.)