Question

This might be one of those silly question where, once a solution is pointed out, makes you feel pretty stupid wondering how you didn’t see it but I can’t figure out why this part of my app is crashing with EXC_BAD_ACCESS (and no stack trace).

I have a CLLocationManager *locationManager (ivar declared in interface file) that gets created on viewDidLoad if locationServices is enabled:

- (void)viewDidLoad
{
    [super viewDidLoad];
    if ([CLLocationManager locationServicesEnabled])
    [self findUserLocation];
    ...
}

#pragma mark - Location finder methods

- (void)findUserLocation
{
    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers;
    [locationManager startUpdatingLocation];    
}

So the location manager starts updating location and each time and update is found, the delegate method below is called, where I check to see if I should time out or continue looking for my desiredAccuracy:

#pragma mark - CLLocationManager delegates

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    if ([newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp] > 8)
        [self locationManagerTimeOut];
    else if ((newLocation.horizontalAccuracy <= manager.desiredAccuracy) && (newLocation.verticalAccuracy <= manager.desiredAccuracy))
        [self locationManagerLockedPosition];
}

If a position is locked, this method is called:

- (void)locationManagerLockedPosition
{
    [locationManager stopUpdatingLocation];
    locationManager.delegate = nil;
    [locationManager release], locationManager = nil;
    NSLog (@"add results to view");
}

If it times out, this is the method called:

- (void)locationManagerTimeOut
{
    [locationManager stopUpdatingLocation];
    locationManager.delegate = nil;
    [locationManager release], locationManager = nil;
    NSLog (@"Time out!");
}

Problem is, in either case (time out or locked position), I get the NSLog output in the console and then 2 secs later the app crashes??

Interesting thing is, if I comment out my [locationManager release]... line, everything works fine but WHY? Also if I move the [locationManager release] to my dealloc method, no crashes either!

Am I missing something basic here?

Thanks!

Rog

Answer 1

I had the same issue and there’s probably some problem in the depths of CLLocationManager. Fixed by doing:

[locationManager stopUpdatingLocation];
[self performSelector:@selector(discardLocationManager) onThread:[NSThread currentThread] withObject:nil waitUntilDone:NO];

and in discardLocationManager do:

- (void) discardLocationManager
{

  locationManager.delegate = nil;
  [locationManager release];

}