Implementing UINavigationController/UITabBarController support for shouldAutorotate without subclassing or extending.

shouldAutorotate_nonintrusive.m

// Add this to your app delegate.

// Neither `UINavigationController` nor `UITabBarController` have the slightest decency to ask their
// visible view controller whether IT would like to rotate and just go on and do whatever the hell
// they please. This'll show 'em.
- (NSUInteger)application:(UIApplication *)application supportedInterfaceOrientationsForWindow:(UIWindow *)window {
  UIViewController* topViewController = window.rootViewController;

  do {
    // Navigate modal controllers.
    if (topViewController.presentedViewController) {
      topViewController = topViewController.presentedViewController;
      continue;
    }

    UIViewController* childViewController = nil;
    if ([topViewController isKindOfClass:[UINavigationController class]]) {
      childViewController = [(UINavigationController *)topViewController visibleViewController];
    } else if ([topViewController isKindOfClass:[UITabBarController class]]) {
      childViewController = [(UITabBarController *)topViewController selectedViewController];
    }
    if (childViewController == nil) {
      break;
    }
    topViewController = childViewController;
  } while (1);

  if (topViewController && !topViewController.shouldAutorotate) {
    // Disallow rotation - only allow the current device orientation.
    return (1 << NIInterfaceOrientation());
  } else if (topViewController) {
    return topViewController.supportedInterfaceOrientations;
  } else {
    return UIInterfaceOrientationMaskAll;
  }
}