instantiateViewControllerWithIdentifier和initWithNibName之间有什么区别,除了前者是故事板而后来不是？
UIStoryboard *signupStory = [UIStoryboard storyboardWithName:@"SignupStory" bundle:[NSBundle mainBundle]];
SignupLoginViewController *signUpVC = [signupStory instantiateViewControllerWithIdentifier:@"SignupVC"];
和
SignupLoginViewController *signUpVC = [[SignupLoginViewController alloc] initWithNibName:@"SignupLoginViewController" bundle:[NSBundle mainBundle]];