情节提要：更改情节提要中指定的UINavigation控制器的根视图

Question

I looked over the suggested list, and didn't see anything that seemed to fit my dilemma.

I am writing my first storyboard project. I have a UITabBarController that manages 4 tabs. Each tab has a UINavigationController as its root, and a number of views in each.

One of the navigation stacks is actually a "ring" of 3 view controllers. I use a custom segue to replace the usual "pile-on" of a navigation stack with a simple replacement (I pile one view on).

This works wonderfully. The storyboard and custom segue are just what the doctor ordered.

However, I want to give the user the choice of which of the 3 views they start with (becomes the root of the navigation stack). The storyboard insists on my selecting one of them as the root, so I do. However, at runtime, the user may want the initial view to be different, so I want the navigation stack to have a different view.

In a nib-based app, I'd simply instantiate a new controller from a nib, and replace the current root with that controller.

How do I pick out a controller and do that in a storyboard?

Answer 1

UPDATE: Thanks to a comment in another thread , I was able to simplify this a bit.

OK. I figured it out.

Instead of replacing the root, I simply push the appropriate controller on. This is because changing the root requires re-instantiating the controller, and the fox just ain't worth the chase. This has zero effect on the UX, so we do it this way:

/**************************************************************//**
 \brief Selects the initial search screen, depending on the user's choice.
 *****************************************************************/
- (void)selectInitialSearchAndForce:(BOOL)force         ///< If YES, then the screen will be set to the default, even if we were already set to one.
{
    UITabBarController  *tabController = (UITabBarController *)self.window.rootViewController;

    [tabController setSelectedIndex:0]; // Set the tab bar to the search screens.

    if ( force )
        {
        UIStoryboard    *st = [tabController storyboard];

        [[searchNavController navigationController] popToRootViewControllerAnimated:NO];

        UIViewController    *newSearch = nil;

        switch ( [[BMLT_Prefs getBMLT_Prefs] searchTypePref] )
            {
            case _PREFER_MAP_SEARCH:
            if ([[UIDevice currentDevice] userInterfaceIdiom] != UIUserInterfaceIdiomPad)   // The map and simple searches are combined, on the iPad.
                {
                newSearch = [st instantiateViewControllerWithIdentifier:@"map-search"];
                }
            break;

            case _PREFER_ADVANCED_SEARCH:
            newSearch = [st instantiateViewControllerWithIdentifier:@"advanced-search"];
           break;
            }

        if ( newSearch )    // We push the controller, as opposed to changing the root, because it's easier, and doesn't violate any of our ground rules.
            {
            [[searchNavController navigationController] pushViewController:newSearch animated:NO];
            // In the case of the iPad, we use a standard navbar push, so we need to prime the simple view to properly populate the Advanced view back button.
            if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad)
                {
                UIViewController    *simpleViewController = [[[searchNavController navigationController] viewControllers] objectAtIndex:0];

                simpleViewController.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:NSLocalizedString([[simpleViewController navigationItem] title], nil)
                                                                                                         style:UIBarButtonItemStyleBordered
                                                                                                        target:nil
                                                                                                        action:nil];
                }
            }
        }
}