Using background location to keep NSTimer running - swift

Question

I'm trying to keep a NSTimer running in the background for a long period of time (multiple hours) but ofc Apple has strict rules about background execution (10 mins), but they do allow certain things such as audio and location to play in the background.
I was wondering how I could use location manager to keep a NSTimer running, basically the user sets an 'alarm' and i need it to go off at that time, so the location manager keeps the timer alive or something similar
Not sure how to approach I have this so far in my app delegate
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, CLLocationManagerDelegate{
var window: UIWindow?
var locationManager = CLLocationManager()
func update() {
var backgroundMusic:AVAudioPlayer
backgroundMusic = self.setupAudioPlayerWithFile("music", type:"mp3")
backgroundMusic.volume = 1
backgroundMusic.prepareToPlay()
backgroundMusic.play()
println("we made!")
}
func setupAudioPlayerWithFile(file:NSString, type:NSString) -> AVAudioPlayer {
//1
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
var path = NSBundle.mainBundle().pathForResource(file as String, ofType: type as String)
var url = NSURL.fileURLWithPath(path!)
//2
var error: NSError?
//3
var audioPlayer:AVAudioPlayer?
audioPlayer = AVAudioPlayer(contentsOfURL: url, error: &error)
//4
return audioPlayer!
}
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// Override point for customization after application launch.
if NSUserDefaults.standardUserDefaults().boolForKey(kLoadedOnceKey) == false {
NSUserDefaults.standardUserDefaults().setBool(true, forKey: kLoadedOnceKey)
NSUserDefaults.standardUserDefaults().setBool(false, forKey: kShouldCapitalizeTaskKey)
NSUserDefaults.standardUserDefaults().setBool(false, forKey: kShouldCompleteNewTodoKey)
NSUserDefaults.standardUserDefaults().synchronize()
}
application.registerUserNotificationSettings(UIUserNotificationSettings(forTypes: UIUserNotificationType.Sound | UIUserNotificationType.Alert |
UIUserNotificationType.Sound, categories: nil
))
return true
}
func applicationWillResignActive(application: UIApplication) {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
func applicationDidEnterBackground(application: UIApplication) {
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
self.locationManager.delegate = self
self.locationManager.startUpdatingLocation()
}
func applicationWillEnterForeground(application: UIApplication) {
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
func applicationDidBecomeActive(application: UIApplication) {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
func applicationWillTerminate(application: UIApplication) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
// Saves changes in the application's managed object context before the application terminates.
self.saveContext()
}
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "KashishGoel.Photo_Alarm" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as! NSURL
}()
lazy var managedObjectModel: NSManagedObjectModel = {
// The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
let modelURL = NSBundle.mainBundle().URLForResource("Photo_Alarm", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("Photo_Alarm.sqlite")
var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
coordinator = nil
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error
error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
func locationManager(manager: CLLocationManager!, didUpdateToLocation newLocation: CLLocation!, fromLocation oldLocation: CLLocation!) {
self.sendBackgroundLocationToServer(newLocation);
}
func sendBackgroundLocationToServer(location: CLLocation) {
var bgTask = UIBackgroundTaskIdentifier()
bgTask = UIApplication.sharedApplication().beginBackgroundTaskWithExpirationHandler { () -> Void in
UIApplication.sharedApplication().endBackgroundTask(bgTask)
}
println(location.coordinate.latitude)
if (bgTask != UIBackgroundTaskInvalid)
{
UIApplication.sharedApplication().endBackgroundTask(bgTask);
bgTask = UIBackgroundTaskInvalid;
}
}
}
I want to be able to call the update function when the NSTimer goes off, any advice on how to set this NSTimer?

Answer 1

Using the NSTimer for an alarm probably isn't the best choice. As you are finding out, you can't keep it running forever not to mention if the user terminates your app. Also, Apple is very strict on what apps get approved when it comes to running location updates in the background. I have first hand experience with this. I would recommend you look at using Local Notifications instead to set your alarm then you will not have to worry about keeping a timer running and it will be much more reliable.