swift 获得UIStoryboard的 控制器

                    let storyboard = UIStoryboard(name: "Main", bundle: nil)
                    guard let viewController = storyboard.instantiateViewController(withIdentifier: "loginViewController") as? LoginViewController
                        else { return }
                    viewController.modalPresentationStyle = .formSheet
                    viewController.isModalInPresentation = true
                    self.window?.rootViewController?.present(viewController, animated: true, completion: nil)