I presented a login screen as follows modally. Correct me if I am not right.
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@\"Main\" bundle:nil]
Swift 3, 3.1, 4, 4.2 (as of January, 2021)
var storyboard = UIStoryboard(name: "Main", bundle: nil)
var loginViewController = storyboard.instantiateViewController(withIdentifier: "login")
loginViewController.modalTransitionStyle = .crossDissolve
self.present(loginViewController, animated: true, completion: nil)