Why does LocationManager calls startUpdatingLocation multiple times?

Question

Why is the Location Manager calling startUpdatingLocation more than once? Sometimes it is calling once, other times it is calling it three times. I don't know why; maybe you could help me. I have this code from GitHub.

import UIKit
import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate
{

    let locationManager = CLLocationManager()

    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.locationManager.delegate = self
        self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
        self.locationManager.requestWhenInUseAuthorization()
        self.locationManager.startUpdatingLocation()
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        CLGeocoder().reverseGeocodeLocation(manager.location!, completionHandler: {(placemarks, error) -> Void in

            if (error != nil)
            {
                print("Error: " + error!.localizedDescription)
                return
            }

            if placemarks!.count > 0 {
                if let pm = placemarks?.first {
                    self.displayLocationInfo(pm)
                }
            }
            else
            {
                print("Error with the data.")
            }
        })
    }

    func displayLocationInfo(placemark: CLPlacemark)
    {

        self.locationManager.stopUpdatingLocation()
        print(placemark.locality)
        print(placemark.postalCode)
        print(placemark.administrativeArea)
        print(placemark.country)
    }

    func locationManager(manager: CLLocationManager, didFailWithError error: NSError)
    {
        print("Error: " + error.localizedDescription)
    }

}

Answer 1

Yes, this is standard behavior. When you start location services you will generally receive a series of increasingly accurate CLLocation updates (i.e. with horizontalAccuracy decreasing over time) as the device "warms up". For example, it might start reporting location information that it might already have on the basis of cell towers, but as the GPS chip gets more information by which it can better triangulate your location, it will give you updates. Etc.

If you want to reduce this behavior, you can use a combination of a larger distanceFilter, a lower desiredAccuracy, or call stopUpdatingLocation once you get a location that you will geocode.

Right now you are calling stopUpdatingLocation, but you're doing it from the asynchronously called closure of reverseGeocodeLocation. This means that more location updates are able to slip in before the completion handler of reverseGeocodeLocation is called. If you call stopUpdatingLocation synchronously (e.g. before reverseGeocodeLocation), then you will avoid this behavior.