导航条返回到特定的控制器
//取得导航控制器的某一个控制器
UIViewController *VC=[[self.navigationController viewControllers]objectAtIndex:self.navigationController.viewControllers.count-3];
[self.navigationController popToViewController:VC animated:YES];
//取得导航控制器的某一个控制器
UIViewController *VC=[[self.navigationController viewControllers]objectAtIndex:self.navigationController.viewControllers.count-3];
[self.navigationController popToViewController:VC animated:YES];