为什么此代码在iOS 5.1中崩溃而不在iOS 6中崩溃？

Question

This code is called from inside my Navigation views inside my Settings tab. It crashes on the last line in iOS 5.1 but NOT iOS 6. Why?

else if (indexPath.section == 0 && [[settingsArray objectAtIndex:indexPath.row] isEqualToString:@"Unlock Premium Features"])
    {
        InAppViewController *inappController = [[InAppViewController alloc] initWithNibName:@"InAppViewController" bundle:nil];
        inappController.titleString = @"Upgrade to Pro.";
        EditNavController *navController = [[EditNavController alloc] initWithRootViewController:inappController];
        [self.navigationController presentModalViewController:navController animated:NO];
    }

It crashes on:

[self.navigationController presentModalViewController:navController animated:NO];

Here is the crash:

*** Terminating app due to uncaught exception 'NSInvalidUnarchiveOperationException', reason: 'Could not instantiate class named NSLayoutConstraint'

Answer 1

if you are using autolayout (if you created a new nib its on by default) in the view being presented, it will crash because auto layouts were only introduced in ios 6.