iOS 多级页面，返回到当前层级前2级页面

NSInteger index = (NSInteger)[[self.navigationController viewControllers] indexOfObject:self];
if (index > 2) {
       [self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:(index-2)] animated:YES];
}else{
       [self.navigationController popToRootViewControllerAnimated:YES];
}