How do I get a background location update every n minutes in my iOS application?

I found a solution to implement this with the help of the Apple Developer Forums:

• Specify location background mode
• Create an NSTimer in the background with UIApplication:beginBackgroundTaskWithExpirationHandler:
• When n is smaller than UIApplication:backgroundTimeRemaining it will work just fine. When n is larger, the location manager should be enabled (and disabled) again before there is no time remaining to avoid the background task being killed.

This works because location is one of the three allowed types of background execution.

Note: I lost some time by testing this in the simulator where it doesn't work. However, it works fine on my phone.

On iOS 8/9/10 to make background location update every 5 minutes do the following:

1. Go to Project -> Capabilities -> Background Modes -> select Location updates

2. Go to Project -> Info -> add a key NSLocationAlwaysUsageDescription with empty value (or optionally any text)

3. To make location working when your app is in the background and send coordinates to web service or do anything with them every 5 minutes implement it like in the code below.

I'm not using any background tasks or timers. I've tested this code with my device with iOS 8.1 which was lying on my desk for few hours with my app running in the background. Device was locked and the code was running properly all the time.

@interface LocationManager () <CLLocationManagerDelegate>
@property (strong, nonatomic) CLLocationManager *locationManager;
@property (strong, nonatomic) NSDate *lastTimestamp;

@end

@implementation LocationManager

+ (instancetype)sharedInstance
{
    static id sharedInstance = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
        LocationManager *instance = sharedInstance;
        instance.locationManager = [CLLocationManager new];
        instance.locationManager.delegate = instance;
        instance.locationManager.desiredAccuracy = kCLLocationAccuracyBest; // you can use kCLLocationAccuracyHundredMeters to get better battery life
        instance.locationManager.pausesLocationUpdatesAutomatically = NO; // this is important
    });

    return sharedInstance;
}

- (void)startUpdatingLocation
{
    CLAuthorizationStatus status = [CLLocationManager authorizationStatus];

    if (status == kCLAuthorizationStatusDenied)
    {
        NSLog(@"Location services are disabled in settings.");
    }
    else
    {
        // for iOS 8
        if ([self.locationManager respondsToSelector:@selector(requestAlwaysAuthorization)])
        {
            [self.locationManager requestAlwaysAuthorization];
        }
        // for iOS 9
        if ([self.locationManager respondsToSelector:@selector(setAllowsBackgroundLocationUpdates:)])
        {
            [self.locationManager setAllowsBackgroundLocationUpdates:YES];
        }

        [self.locationManager startUpdatingLocation];
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    CLLocation *mostRecentLocation = locations.lastObject;
    NSLog(@"Current location: %@ %@", @(mostRecentLocation.coordinate.latitude), @(mostRecentLocation.coordinate.longitude));

    NSDate *now = [NSDate date];
    NSTimeInterval interval = self.lastTimestamp ? [now timeIntervalSinceDate:self.lastTimestamp] : 0;

    if (!self.lastTimestamp || interval >= 5 * 60)
    {
        self.lastTimestamp = now;
        NSLog(@"Sending current location to web service.");
    }
}

@end