Update: I have decided to go a different route with my problem.
Instead of trying to reuse the same UIViewController directly, I use two vanilla UIViewControllers that are set as rootViewControllers. In their loadView methods, they make a call to [storyboard instantiateViewControllerWithIdentifier:]
to get the former UIViewController and set their views to the controller's view. This is probably the preferred approach anyway, since I need to set several variables and delegates.
I have a UIStoryBoard with a UITabBarController as the entry point connected with two UINavigationControllers. Each of those share a common UIViewController as their root view controller. When the app starts, the first UITabBarItem is selected and the view loads as-expected. However, when I select the second UITabBarItem, the same view is not visible. I see the UINavigationBar with a black background. Am I doing something incorrect with the Storyboard interface, or do I need to manually instantiate the UIViewController via each UINavigationController's method--loadView for instance?
The root view controller is simply the view controller that sits at the bottom of the navigation stack. You can access the navigation controller's array of view controllers through its viewControllers property. To access the root view controller, we ask for the first item of the array of view controllers.
A UIViewController is an object which manages the view hierarchy of the UIKit application. The UIViewController defines the shared behavior and properties for all types of ViewController that are used in the iOS application. The UIViewController class inherits the UIResponder class.
Strangely this is a question that no one else is asking. As far as I know it is not possible to share the rootViewController which I think is without a doubt a bug since when you inspect the connection on the storyboard you can see that the view controller is connected to both navigation controllers. I consider this a flaw in storyboarding because duplicating viewControllers and reapplying all of their connections is quite error prone and makes the storyboards overly complex.
I see your solution to the problem. Workarounds like this make me question if the current storyboard functionality in iOS is ready for creating apps. I think that there is a conceptual problem with the storyboards, Apple needs to decide if a viewController on a storyboard represents an instance or if it represents just the class, right now it is not consistent as you can see that multiple segues can actually point to the same viewController but in reality each segue has its own instance, why this is not also followed for rootViewController connections?, I don't know.
Just as a note, with your solution take into account the following from Apple's documentation:
"Important A view controller is the sole owner of its view and any subviews it creates. It is responsible for creating those views and for relinquishing ownership of them at the appropriate times, including during low-memory conditions and when the view controller itself is released. If you use a storyboard or a nib file to store your view objects, each view controller object automatically gets its own copy of these views when the view controller asks for them. However, if you create your views manually, you should never use the same view objects with multiple view controllers."
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIViewController_Class/Reference/Reference.html
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