objective c - iOS background fetch custom interval

Question

I read all Apple documentation about background fetch and currently I'm using it like this:

[[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:minimumBackgroundFetchInterval];

I let OS to decide when to perform background fetch, but if I set it like this:

[[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:21600];

Does that mean that fetch will happen every 6h?

Answer 1

I did some experiment on iOS10 and iPhone6Plus, giving "UIApplicationBackgroundFetchIntervalMinimum" interval. (of course I invoked some network-related method to give iOS a hint that app is really working... and invoking completionHandler(UIBackgroundFetchResultNewData); )

I got: (run all night)

00:35 01:03 01:31 01:59 02:27 02:55 03:13 03:23 03:51 04:19 04:35 05:04 05:25 05:59 06:27 06:56

so Delta varies from 10 to 34 mins.