goal c – Tab bar doesn’t seem in iOS

I’m making an attempt to make an iOS hybrid app, however I am caught on step one;
my app doesn’t present its tab bar like this pic tab bar not present

My debug consequence reveals in UITabBarController the self.tabBar.subviews.subviews is empty when i attempt to traverse it, it throw an exception;error

there’s the code

// AppDelegate.m
- (BOOL)utility:(UIApplication *)utility didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    BaseTabbarViewController *tabbarVC = [[BaseTabbarViewController alloc]init];
    self.window.rootViewController = tabbarVC;
    [self.window makeKeyAndVisible];
    return YES;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    self.tabBar.barTintColor = [UIColor whiteColor];
    [self setupChildVC];
    self.indexFlag = 0;
}
- (void)setupChildVC {
    OKRWebViewController *okrMainVC = [[OKRWebViewController alloc] initWithConfig:@"http://192.168.2.183:8080/OKRMain?enable_bounds=0&hide_scroll_bar=1"];
    [self setupTabbarItem:okrMainVC.tabBarItem title:@"main" titleSize:12 titleFontName:@"HeiTi SC" normalTitleColor:[UIColor grayColor] selectedTitleColor:[UIColor purpleColor] normalImage:@"tabbar_about_normal" selectedImage:@"tabar_select2"];
    OKRWebViewController *okrMainVC2 = [[OKRWebViewController alloc] initWithConfig:@"http://192.168.2.183:8080/OKRMain?enable_bounds=0&hide_scroll_bar=1"];
    [self setupTabbarItem:okrMainVC2.tabBarItem title:@"order" titleSize:12 titleFontName:@"HeiTi SC" normalTitleColor:[UIColor grayColor] selectedTitleColor:[UIColor purpleColor] normalImage:@"tabbar_order_normal" selectedImage:@"tabar_select2"];
    BaseNavigationController *navA = [[BaseNavigationController alloc]initWithRootViewController:okrMainVC];
    BaseNavigationController *navB = [[BaseNavigationController alloc]initWithRootViewController:okrMainVC2];
    self.viewControllers = @[navA,navB];
}
- (void)upAnimationWithIndex:(NSInteger)index {
    NSMutableArray *tabBarButtonImageArray = [NSMutableArray array];
    for (UIControl *tabBarButton in self.tabBar.subviews) {
        if ([tabBarButton isKindOfClass:NSClassFromString(@"UITabBarButton")]) {
            for (UIView *imageView in tabBarButton.subviews) { // throw exception
                if ([imageView isKindOfClass:NSClassFromString(@"UITabBarSwappableImageView")]) {
                    [tabBarButtonImageArray addObject:imageView];
                }
            }
        }
    }
}

discovered some demos and forked the code however that did not work both, I am unsure if completely different configurations would trigger the problem;

https://github.com/PrincessSmall/TabBarConteollerDemo#tabbarconteollerdemo