Some App Actions Breaking TImer? - ios

Question

I have a Timer that i run on my app, it uses a save and reload feature for when the user leaves the view and returns to the view. However if i go to a different tab on my app, the actions needed for that tab seem to break the timer.
Would this be due to thread usage in the app and the coredata of the other tab breaking the timers counting? Here is my timer code
Update 2: Here is my revised timer code in full...
// MARK: - SETTING UP SETS & TIMERS
func createStopTimeForRestFromUserTime(userTime: Int) -> Date {
let calendar = Calendar.current
let stopDate = calendar.date(byAdding: .second, value: userTime, to: Date())
return stopDate!
}
func createTimer(stopDate: Date) {
print("CONSTRUCTING A TIMER")
userDefaults.set(stopDate, forKey: "setStopDate")
restTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(RestController.updateRestTimer), userInfo: nil, repeats: true)
}
func updateRestTimer() {
let presentTime = Date()
let stoppedTime = UserDefaults.standard.object(forKey: "setStopDate") as? Date
if stoppedTime?.compare(presentTime) == ComparisonResult.orderedDescending {
restRemainingCountdownLabel.text = dateComponentsFormatter.string(from: presentTime, to: stoppedTime!)
} else {
self.stopTimer()
print("THE TIMER IS NOW FINISHED")
}
}
func stopTimer() {
self.restTimer.invalidate()
}
// MARK: - CONFIGURE TIMER ON OPEN / CLOSE
override func viewWillDisappear(_ animated: Bool) {
print("VIEWWILLDISAPPEAR WAS CALLED")
stopTimer()
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "ViewDidChangeNotification"), object: NSDate())
}
func handleResumedTime(disappTime: NSDate) {
let disappearedTime = disappTime
let resumeTime = NSDate()
if disappearedTime.compare(resumeTime as Date) == ComparisonResult.orderedDescending {
print("RESUMING THE TIMER")
self.createTimer(stopDate: disappearedTime as Date)
} else {
print("TIMER HAS FINISHED")
stopTimer()
}
}
func handleTimerCallback(notification: NSNotification) {
if let date = notification.object as? NSDate {
self.handleResumedTime(disappTime: date)
}
}
Code in an alternate VC id switch between which is causing breakage:
override func viewDidLoad() {
NotificationCenter.default.addObserver(self, selector: #selector(RoutineController.handleTimerCallback(notification:)), name: NSNotification.Name(rawValue: "ViewDidChangeNotification"), object: nil)
}
override func viewWillDisappear(_ animated: Bool) {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "ViewDidChangeNotification"), object: NSDate())
}
func handleTimerCallback(notification: NSNotification) {
let date = notification.object
print("Object is \(date)")
}
EDIT: Added the updated handleResumed func and console print out when changing tab and changing back again...
func handleResumedTime(disappTime: NSDate) {
let disappearedTime = disappTime as Date
let resumeTime = NSDate() as Date
print("ATTEMPTING RESUME")
print(disappearedTime)
print(resumeTime)
if resumeTime.compare(disappearedTime) == ComparisonResult.orderedAscending {
print("RESUMING THE TIMER")
self.createTimer(stopDate: disappearedTime)
} else {
print("TIMER HAS FINISHED")
stopTimer()
}
}

Answer 1

Try comparing the timers in milliseconds using DateFormatter and passing data between controllers using Notifications.
This function is called every time you switch tabs. It invalidates the timer, stops the ticking, and saves the time in milliseconds.
override func viewWillDisappear(_ animated: Bool) {
restTimer.invalidate()
let df = DateFormatter()
df.dateFormat = "y-MM-dd H:m:ss.SSSS"
let disappearingDate = Date()
let disappearingDateInMilliseconds = df.string(from: disappearingDate)
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "kViewDidChangeExampleNotification"), object: disappearingDateInMilliseconds)
}
/* add your Notification observers in each view controller */
override func viewDidLoad() {
NotificationCenter.default.addObserver(self, selector: #selector(ViewController.handleTimerCallback(notification:)), name: NSNotification.Name(rawValue: "kViewDidChangeExampleNotification"), object: nil)
}
You need to define the function that will handle the notifications in each controller:
func handleTimerCallback(notification: NSNotification) {
if let dateString = notification.object as? String {
print("Object is an String: \(notification.object)")
resumeTimerWithDate(dateString)
} else {
print("Object is not of type String: \(notification.object)")
}
}
Quick example comparing Dates in Swift by milliseconds:
func resumeTimerWithDate(dateString: String) {
let df = DateFormatter()
df.dateFormat = "y-MM-dd H:m:ss.SSSS"
let secondDate = Date()
let secondDateToStr = df.string(from: secondDate)
if dateString < secondDateToStr {
print("RESUMING THE TIMER")
let resumeDate = df.date(from: dateString)
self.createTimer(resumeDate)
} else {
print("TIMER HAS FINISHED")
}
}
Other things to consider: You may want to add some print statements for debugging / sanity check because some functions may be firing before others. For example, rather than posting the notification in viewWillDisappear, you can try posting it in viewDidDisappear, or using prepare(for segue:).