popToViewController用法，直接初始化一個VC,而後pop會崩潰。

[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:2] 
animated:YES];
或

for (UIViewController *temp in self.navigationController.viewControllers) {
           if ([temp isKindOfClass:[你要跳轉到的Controller class]]) {
              [self.navigationController popToViewController:temp animated:YES];
           }
       }