iOS不同模式返回根视图的方法

[self.navigationController popToViewController: [self.navigationController.viewControllers objectAtIndex: ([self.navigationController.viewControllers count] - 3)] animated:YES];

[self.navigationController popToRootViewControllerAnimated:YES];

if ([self respondsToSelector:@selector(presentingViewController)]){
self.presentingViewController.view.alpha = 0;
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:YES completion:nil];
}else {
self.parentViewController.view.alpha = 0;
[self.parentViewController.parentViewController dismissViewControllerAnimated:YES completion:nil];
}