Refreshing location then running NSXMLParser - ios

Question

My app (1) gets the user's location then (2) parses XML based on that location data. From load, the app works great. But I would like to get updated XML based on a change of location when the user taps the refresh button. I've tried several versions of this but can't get to work. I've included the portion of my code I think is relevant to this question (I think it's a timing issue). On tapping the refresh button, the location updates but the old XML is loaded:
class Myclass: UIPageViewController, UIPageViewControllerDataSource, CLLocationManagerDelegate, NSXMLParserDelegate {
let locationManager = CLLocationManager()
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters
locationManager.requestWhenInUseAuthorization()
//locationManager.requestLocation()
}
override func viewWillAppear(animated: Bool) {
switch CLLocationManager.authorizationStatus() {
case .AuthorizedWhenInUse, .AuthorizedAlways:
busyAlertController.display()
locationManager.requestLocation()
print("Authorized")
case .NotDetermined:
locationManager.requestWhenInUseAuthorization() // or request always if you need it
print("Not Determined")
case .Restricted, .Denied:
print("Restricted or Denied")
self.dismissViewControllerAnimated(true, completion: nil)
let alertController = UIAlertController(
title: "Background Location Access Disabled",
message: "We need to know your location to show you the correct forecast, please open this app's settings and set location access to 'When in Use' or 'Always'.",
preferredStyle: .Alert)
let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)
alertController.addAction(cancelAction)
let openAction = UIAlertAction(title: "Open Settings", style: .Default) { (action) in
if let url = NSURL(string:UIApplicationOpenSettingsURLString) {
UIApplication.sharedApplication().openURL(url)
}
}
alertController.addAction(openAction)
self.presentViewController(alertController, animated: true, completion: nil)
}
}
// MARK: UIPageViewControllerDataSource & UIPageViewControllerDelegate
// MARK: - CLLocationManagerDelegate
func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
if (status == .AuthorizedAlways) || (status == .AuthorizedWhenInUse) {
locationManager.requestLocation()
}
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if let location = locations.first {
let lat = "\(location.coordinate.latitude)"
let lon = "\(location.coordinate.longitude)"
let url = baseURL + lat + "&lon=" + lon + suffixURL
guard let urlAsNSURL = NSURL(string: url) else {return}
NWSURL = urlAsNSURL
runParser()
} else {
//TODO:
}
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
print("Error finding location: \(error.localizedDescription)")
showAlert("Location Problem", message: "We're having trouble finding your location, please try again.")
}
//XMLParser Methods
func parserDidEndDocument(parser: NSXMLParser){
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.showVC()
})
}
func runParser() {
guard let url = URL else {
return}
guard let parser = NSXMLParser(contentsOfURL: url) else {return}
parser.delegate = self
parser.parse()
}
#IBAction func refresh(sender: UIBarButtonItem) {
locationManager.requestLocation()
//runParser()
}
}

Answer 1

The locations array which was passed into locationManager:didUpdateLocations: may contain more than one location in case updates were deferred or multiple locations arrived before they could be delivered.
Since it is organized in the order in which the updates occurred, the most recent location update is at the end of the array.
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if let location = locations.last {
...
}
}

Answer 2

The problem was that I wasn't clearing out a variable (array) after the NSXMLParser was done, and so I was appending over the stale data, yet since the stale data was first it was displaying in my UI and made it VERY hard to detect the problem until I printed to the console and saw the multiple arrays. I've done something similar before so note to anyone implementing NSXMLParser: make sure that you clear out the variable that you are using to store data in didEndElement.