swift和OC去掉导航栏下面的线

      //去掉导航栏下面的线  oc

    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"white_bg"] forBarMetrics:UIBarMetricsDefault];

    [self.navigationController.navigationBar setShadowImage:[UIImage new]];

      //去掉导航栏下面的线  swift

        self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: UIBarMetrics.default)

        self.navigationController?.navigationBar.shadowImage = UIImage()