let storyboard = UIStoryboard(name: "Main", bundle: nil)
        //let vc = self
        let vc = storyboard.instantiateViewController(withIdentifier: "loginView") as! RegistrationViewController
        self.present(vc, animated: true, completion: nil)

2017-07-24 16:39:48.135 XXX [8689:286531] Warning: Attempt to present <XXX.RegistrationViewController: 0x7f8246206280> on <XXX.LaunchAppCheck: 0x7f8243d06bd0> whose view is not in the window hierarchy!