单击UITabBarController的选项卡栏，调用不同的viewControllers

如果要基于自定义逻辑替换所选选项卡上的根视图控制器，请尝试使用UITabBarController setViewControllers:animated:方法。

您可以执行以下操作：

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
    if (tabBarController.selectedIndex == 1 && tabBarController.viewControllers.count > tabBarController.selectedIndex) {
        BOOL shouldShowContactVC = (BOOL)(rand() % 2);
        NSMutableArray *viewControllers = [[tabBarController viewControllers] mutableCopy];
        UIStoryboard *main = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
        UIViewController *newVC = nil;
        if (shouldShowContactVC) {
            newVC = [main instantiateViewControllerWithIdentifier:@"ContactUsVC"];
        } else {
            newVC = [main instantiateViewControllerWithIdentifier:@"AboutUsVC"];
        }
        if (newVC) {
            [viewControllers replaceObjectAtIndex:tabBarController.selectedIndex withObject:newVC];
            newVC.tabBarItem = viewController.tabBarItem;
            [tabBarController setViewControllers:viewControllers animated:YES];
        }
    }
}