Navigation stack monitoring

Question

Can anyone tell me why this comparison keeps making my app freeze and crash?

NSArray *viewControllerArray = [controlFromMap.navigationController viewControllers];
NSUInteger parentViewControllerIndex = [viewControllerArray count] - 3 // or - whatever;
NSLog(@"Parent view controller: %@", [viewControllerArray objectAtIndex:parentViewControllerIndex]);



if([[[viewControllerArray objectAtIndex:parentViewControllerIndex]stringValue] isEqualToString: @"FromAddressController"]){

    _mapView.showsUserLocation = NO;
}
else{

_mapView.showsUserLocation = YES;
}

Answer 1

If you add:

NSLog(@"parentViewControllerIndex: %d", parentViewControllerIndex);

after the line:

NSUInteger parentViewControllerIndex = [viewControllerArray count] - 3;

What value do you see in the console?

Answer 2

Also, this line:

if([[[viewControllerArray objectAtIndex:parentViewControllerIndex]stringValue] isEqualToString: @"FromAddressController"]){

looks suspicious to me.

I checked the documentation and the UIViewController class does not appear to have a -stringValue method. So you probably will get an unrecognized selector exception and your application will crash.

Perhaps you mean nibName instead of stringValue?

Answer 3

[viewControllerArray objectAtIndex:parentViewControllerIndex] should return an instance of UIViewController subclass. Make sure it responds to -stringValue or (assuming FromAddressController is a class name) make it so:

if([[viewControllerArray objectAtIndex:parentViewControllerIndex] class] == [FromAddressController class])