Question

I read that it is bad to have such structure in an iOS application. But what if an application has a lot of UINavigationControllers and UITabBarControllers. But one UINavigationBar and one UITabBar are always displayed only? Other UINavigationBars and UITabBars are hidden.

EDITED

For example, in navigation-based application I call this code:

- (IBAction)openTabsController:(id)sender {        

    tabOneController *tabOneViewContr = [[[tabOneController alloc] initWithNibName:@"tabOneController" bundle:nil] autorelease];
    UINavigationController *tabOneNavContr = [[UINavigationController alloc] initWithRootViewController:tabOneViewContr];

    tabTwoController *tabTwoViewContr = [[[tabTwoController alloc] initWithNibName:@"tabTwoController" bundle:nil] autorelease];
    UINavigationController *tabTwoNavContr = [[UINavigationController alloc] initWithRootViewController:tabTwoViewContr];


    UITabBarController *tabContr = [[[UITabBarController alloc] init] autorelease];
    tabContr.viewControllers = [NSArray arrayWithObjects:tabOneNavContr,tabTwoNavContr, nil];
    sel.navigationController.navigationBar.hidden = YES;
    [self.navigationController pushViewController:tabContr animated:YES];
}

After calling of this method I have two UINavigationControllers and one UITabBarController. At the same time I have one UINavigationBar and one UITabBar on a screen.

EDITED

Approximate scheme.

From The beginning we have an UINavigationController which allows to navigate between the views (circles). Then after pushing an UITabBar appears and allows to switch between the views. A rectangle with two little rects is a view with a UITabBar with 2 UITabBarItem s. When we presss any UITabBarItem another UIView appears. In this UIView we can press some button which calls another view with another UITabBar. Current UITabBar is visible after pushing if it is not hidden with another UITabBar.
is it more clear now?
The code above works almost perfect (except of some animations and not including Apple’s limitations)

Answer 1

Gargo,

I’m not sure I understood your question but the apple documentation is clear. If you use - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated it says that viewController:

cannot be an instance of tab bar controller and it must not already be
on the navigation stack.

Since you do

[self.navigationController pushViewController:tabContr animated:YES];

you are pushing a tab bar controller instance within the navigation stack.

If you add the structure that you would achieve maybe I can help you to find another solution.

Hope that helps.