“Unrecognized selector sent to instance” error

Question

Part of my AppDelegate code is:

UITabBarController *tabBarController 
    = (UITabBarController *)self.window.rootViewController;

UINavigationController *na         


        

Answer 1

I met the same issue, because I followed the steps by the author, but

UINavigationController *navigationController 
    = [[tabBarController viewControllers] objectAtIndex:0];

this is what which made the crash, because navigationController is not at index=0, I did exchange the locations of the two tab bar items, then it works.