获取navigationController中的控制器

@implementation UIViewController (UIViewControllerExt)

- (void)popViewController:(NSString *)controllerStr
{
    for (UIViewController *vc in self.navigationController.viewControllers) {
        if ([vc isKindOfClass:[NSClassFromString(controllerStr) class]]) {
            [self.navigationController popToViewController:vc animated:YES];

        }
    }
}