I have seen this line of code
UIApplication.sharedApplication() .openURL(NSURL(string:"prefs:root=General")!)
is not working, it didn't work for me in ios10/ Xcode 8, just a small code difference, please replace this with
UIApplication.sharedApplication().openURL(NSURL(string:"App-Prefs:root=General")!)
Swift3
UIApplication.shared.openURL(URL(string:"prefs:root=General")!)
Replace with
UIApplication.shared.openURL(URL(string:"App-Prefs:root=General")!)
Hope it helps. Cheers.