UINavigationController cann't work fine

[likid1412]

I use a UINavationController to push the first view controller, and then show the second one with this animation, when I tap the dismiss button(created by myself), it crashed!! So, I fixed it.
// This method doesn't suppose UINavigation model

• (id) traverseResponderChainForUIViewController {
  id nextResponder = [self nextResponder];
  BOOL isViewController = [nextResponder isKindOfClass:[UIViewController class]];
  BOOL isTabBarController = [nextResponder isKindOfClass:[UITabBarController class]];
  BOOL isNavController = [nextResponder isKindOfClass:[UINavigationController class]]; // Add this
  if (isViewController && !isTabBarController && !isNavController) {
  return nextResponder;
  } else if(isTabBarController){
  UITabBarController *tabBarController = nextResponder;
  return [tabBarController selectedViewController];
  } else if (isNavController)
  {
  // get the last but one, it should be last view controller for the showing view.
  UINavigationController *nav = nextResponder;
  UIViewController *lastButOne = nav.viewControllers[nav.viewControllers.count - 2];
  NSLog(@"array:%@, \n%@",nav.viewControllers, lastButOne);
  return lastButOne;
  } else if ([nextResponder isKindOfClass:[UIView class]]) {
  return [nextResponder traverseResponderChainForUIViewController];
  } else {
  return nil;
  }
  }

The core code is this:
else if (isNavController)
{
// get the last but one, it should be last view controller for the showing view.
UINavigationController *nav = nextResponder;
UIViewController *lastButOne = nav.viewControllers[nav.viewControllers.count - 2];
NSLog(@"array:%@, \n%@",nav.viewControllers, lastButOne);
return lastButOne;
}

[kentnguyen]

Please learn to format and create a proper ticket with full context (iOS version, device, specific use case)