iOS导航栏返回按钮

导航栏返回按钮隐藏：

    override func pushViewController(_ viewController: UIViewController, animated: Bool) {if let vc = self.viewControllers.last {let backItem = UIBarButtonItem()backItem.title = ""vc.navigationItem.backBarButtonItem = backItem}if viewControllers.count > 0 {viewController.hidesBottomBarWhenPushed = true}super.pushViewController(viewController, animated: animated)}

之所以取 self.viewControllers.last 的最后一个，因为可能控制addsubController ,有从subVC 跳转到其他的控制器