ios segmenetcontroller如何去掉边框

直接看代码：
- (void)viewWillAppear:(BOOL)animated {
[self.navigationController.navigationBar setBackgroundImage:[TDUtils createImageWithColor:[UIColor clearColor]] forBarMetrics:UIBarMetricsDefault];
[self.navigationController.navigationBar setBackIndicatorTransitionMaskImage:[TDUtils createImageWithColor:[UIColor clearColor]]];
[self.navigationController.navigationBar setShadowImage:[TDUtils createImageWithColor:[UIColor clearColor]]];

[self.tabBarController.tabBar setBackgroundImage:[TDUtils createImageWithColor:[UIColor clearColor]]];
[self.tabBarController.tabBar setShadowImage:[TDUtils createImageWithColor:[UIColor clearColor]]];
}