iOS开发 多级页面返回到当前层级前2级页面

NSInteger popIndex = (NSInteger)[[self.navigationController viewControllers] indexOfObject:self];

if (popIndex > 2) {

       [self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:(popIndex-2)] animated:YES];

}else{

       [self.navigationController popViewControllerAnimated:YES];

}