I can't update location IOS - ios

Question

I'm trying to get the city name of my location, I use this code:
- (void)viewDidLoad
{
[super viewDidLoad]; CLLocationManager *locationManager =[[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
[locationManager startUpdatingLocation];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
//implementamos los metodos delegados de CLLocationManager.
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
// this creates a MKReverseGeocoder to find a placemark using the found coordinates
CLGeocoder * geoCoder = [[CLGeocoder alloc] init];
[geoCoder reverseGeocodeLocation:newLocation completionHandler:^(NSArray *placemarks, NSError *error) {
NSString * location = ([placemarks count] > 0) ? [[placemarks objectAtIndex:0] locality] : #"Not Found";
_ciudadLabel.text=location;
}];
}
// this delegate method is called if an error occurs in locating your current location
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
NSLog(#"locationManager:%# didFailWithError:%#", manager, error);
}
But when I execute the application, the message that says if I want to allow to get my location disapear suddenly and don't execute:
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
// this creates a MKReverseGeocoder to find a placemark using the found coordinates
CLGeocoder * geoCoder = [[CLGeocoder alloc] init];
[geoCoder reverseGeocodeLocation:newLocation completionHandler:^(NSArray *placemarks, NSError *error) {
NSString * location = ([placemarks count] > 0) ? [[placemarks objectAtIndex:0] locality] : #"Not Found";
_ciudadLabel.text=location;
}];
}
why the location doesn't start?
Thanks