I seriously didn't believe that this concept of having some UIViewController to show before UISplitViewController (login form for example) turns out to be so complicated, until I had to create that kind of view hiearchy.
My example is based on iOS 8 and XCode 6.0 (Swift), so I'm not sure if this problem existed before in a same way, or it's due to some new bugs introduced with iOS 8, but from all of the similar questions I found, I didn't see complete 'not very hacky' solution to this problem.
I'll guide you through some of the things I have tried before I ended up with a solution (at the end of this post). Each example is based on creating new project from Master-Detail template without CoreData enabled.
First try (modal segue to UISplitViewController):
- create new UIViewController subclass (LoginViewController for example)
- add new view controller in storyboard, set it as initial view controller (instead of UISplitViewController) and connect it to LoginViewController
- add UIButton to LoginViewController and create modal segue from that button to UISplitViewController
- move boilerplate setup code for UISplitViewController from AppDelegate's
didFinishLaunchingWithOptions
to LoginViewController's prepareForSegue
This almost worked. I say almost, because after the app is started with LoginViewController and you tap button and segue to UISplitViewController, there is a strange bug going on: showing and hiding master view controller on orientation change is no longer animated.
After some time struggling with this problem and without real solution, I thought that it's somehow connected with that weird rule that UISplitViewController must be rootViewController (and in this case it isn't, LoginViewController is) so I gave up from this not so perfect solution.
Second try (modal segue from UISplitViewController):
- create new UIViewController subclass (LoginViewController for example)
- add new view controller in storyboard, and connect it to LoginViewController (but this time leave UISplitViewController to be initial view controller)
- create modal segue from UISplitViewController to LoginViewController
- add UIButton to LoginViewController and create unwind segue from that button
Finally, add this code to AppDelegate's didFinishLaunchingWithOptions
after boilerplate code for setting up UISplitViewController:
window?.makeKeyAndVisible()
splitViewController.performSegueWithIdentifier("segueToLogin", sender: self)
return true
or try with this code instead:
window?.makeKeyAndVisible()
let loginViewController = splitViewController.storyboard?.instantiateViewControllerWithIdentifier("LoginVC") as LoginViewController
splitViewController.presentViewController(loginViewController, animated: false, completion: nil)
return true
Both of these examples produce same several bad things:
- console outputs:
Unbalanced calls to begin/end appearance transitions for <UISplitViewController: 0x7fc8e872fc00>
- UISplitViewController must be shown first before LoginViewController is segued modally (I would rather present only the login form so the user doesn't see UISplitViewController before logged in)
- Unwind segue doesn't get called (this is totally other bug, and I'm not going into that story now)
Solution (update rootViewController)
The only way I found which works properly is if you change window's rootViewController on the fly:
- Define Storyboard ID for LoginViewController and UISplitViewController,
and add some kind of loggedIn property to AppDelegate.
- Based on this property, instantiate appropriate view controller and after that set it as rootViewController.
- Do it without animation in
didFinishLaunchingWithOptions
but animated when called from the UI.
Here is sample code from AppDelegate:
var loggedIn = false
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
setupRootViewController(false)
return true
}
func setupRootViewController(animated: Bool) {
if let window = self.window {
var newRootViewController: UIViewController? = nil
var transition: UIViewAnimationOptions
// create and setup appropriate rootViewController
if !loggedIn {
let loginViewController = window.rootViewController?.storyboard?.instantiateViewControllerWithIdentifier("LoginVC") as LoginViewController
newRootViewController = loginViewController
transition = .TransitionFlipFromLeft
} else {
let splitViewController = window.rootViewController?.storyboard?.instantiateViewControllerWithIdentifier("SplitVC") as UISplitViewController
let navigationController = splitViewController.viewControllers[splitViewController.viewControllers.count-1] as UINavigationController
navigationController.topViewController.navigationItem.leftBarButtonItem = splitViewController.displayModeButtonItem()
splitViewController.delegate = self
let masterNavigationController = splitViewController.viewControllers[0] as UINavigationController
let controller = masterNavigationController.topViewController as MasterViewController
newRootViewController = splitViewController
transition = .TransitionFlipFromRight
}
// update app's rootViewController
if let rootVC = newRootViewController {
if animated {
UIView.transitionWithView(window, duration: 0.5, options: transition, animations: { () -> Void in
window.rootViewController = rootVC
}, completion: nil)
} else {
window.rootViewController = rootVC
}
}
}
}
And this is sample code from LoginViewController:
@IBAction func login(sender: UIButton) {
let delegate = UIApplication.sharedApplication().delegate as AppDelegate
delegate.loggedIn = true
delegate.setupRootViewController(true)
}
I would also like to hear if there is some better/cleaner way for this to work properly in iOS 8.