One detail view for several UISplitViews

Question

I have 3 UISplitViewControllers with different master views, but they have the same detail view. All of them are connected in Storyboard.

All UISplitViewControllers are nested in UITabBarViewController, so I switch between them via tab bar items.

The problem is, when I switch to another tab (another UISplitViewController) detail view disappears, I see only master view and a place for detail view is filled with dark gray (see pic). I don't want to reload detail view after switching, just leave it as is on the right side of the screen.

I'm not sure what code I need to provide, so if you need any, ask, I'll add it to question.

Thanks for any help!

Answer 1

Cause

My first hypothesis was that the if you share a detail view controller between two distinct UISplitViewControllers, that correspond to two tabs of a UITabController, two separate detail view controllers are created. This is confirmed with a test project with this layout:

Root View Controller is a DetailViewController. When I put a breakpoint inside viewDidLoad(_:), it gets hit twice and printing shows that two different instances of DetailViewController are created:

(lldb) po self
<TestTabSplit.DetailTableViewController: 0x7fbd10eb9cd0>

(lldb) po self
<TestTabSplit.DetailTableViewController: 0x7fbd10ebc700>

Solution

Use a shared container view controller as the detail view controller of the two UISplitViewControllers.

Your new storyboard layout will look like this:

1. Give your detail view controller (in this case a navigation controller), a Storyboard ID:

2. Next, in your app delegate, instantiate the detail view controller:

   // Add a variable to reference from elsewhere.
   var sharedNavigationController: UINavigationController!
   
   func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
       // Override point for customization after application launch.
   
       sharedNavigationController = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("SharedID") as! UINavigationController
       return true
   }
   

3. Finally, the container view controller, ContainerViewController, is just a subclass of UIViewController with the following contents:

   override func viewDidAppear(animated: Bool) {
       super.viewDidAppear(animated)
   
       let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
       let sharedNavigationController = appDelegate.sharedNavigationController
   
       addChildViewController(sharedNavigationController)
       sharedNavigationController.view.frame = view.bounds
       view.addSubview(sharedNavigationController.view)
       sharedNavigationController.didMoveToParentViewController(self)
   }
   

With this setup, you'll find that the same detail view controller instance is share between tabs and modifications in one tab are persisted when you change to a new tab.