方法1 取出当前的导航控制器

// 取出当前的导航控制器
    UITabBarController *tabBarVc = (UITabBarController *)[UIApplication sharedApplication].keyWindow.rootViewController;
    UINavigationController *nav = (UINavigationController *)tabBarVc.selectedViewController;
    [nav pushViewController:web animated:YES];

方法2

            XMGPostWordViewController *postWord = [[XMGPostWordViewController alloc] init];
            XMGNavigationController *nav = [[XMGNavigationController alloc] initWithRootViewController:postWord];
            
            // 这里不能使用self来弹出其他控制器, 因为self执行了dismiss操作
            UIViewController *root = [UIApplication sharedApplication].keyWindow.rootViewController;
            [root presentViewController:nav animated:YES completion:nil];

方法3

- (UIViewController *)ViewController
{
    UIResponder *next = [self nextResponder];
    
    do {
        if ([next isKindOfClass:[UIViewController class]]) {
            return (UIViewController *)next;
        }
        next = [next nextResponder];
    } while (next != nil);
    return nil;
}