presentViewController Warning view is not in the window hierarchy - ios

Question

I am loading LaunchViewController as the root view controller in my AppDelegate's application:didFinishLaunching method:
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:#"LaunchViewController" bundle:nil];
LaunchViewController *launchViewController = [storyboard instantiateInitialViewController];
launchViewController.managedObjectContext = [CurrentSession mainQueueContext];
self.window.rootViewController = launchViewController;
[self.window makeKeyAndVisible];
LaunchViewController communicates with a web server to fetch some data. I am using AFNetworking library for asynchronous communication with the web server. In the success callback after fetching the data, I am presenting the LoginViewController. My understanding is that the callbacks in case of AFNetworking are performed on the main thread. Nevertheless I used performSelectionOnMainThread just to see if that would resolve the issue:
Inside callback:
[self performSelectorOnMainThread:#selector(presentLoginView) withObject:nil waitUntilDone:NO];
presentLoginViewmethod:
- (void)presentLoginView {
LoginViewController *loginViewController = [[LoginViewController alloc] initWithNibName:#"LoginViewController" bundle:nil];
loginViewController.managedObjectContext = self.managedObjectContext;
[self presentViewController:loginViewController animated:YES completion:nil];
}
The login view is not presented and in the console I see following message:
Warning: Attempt to present <LoginViewController: 0x78e47c30> on <LaunchViewController: 0x78eb4a60> whose view is not in the window hierarchy!
:-(
UPDATE
I put a breakpoint in viewDidLoad, viewDidUnload, viewWillAppear and viewDidAppear methods of the LoginViewController. viewDidLoad was hit. Others were not.
Why would the view get loaded but not appear?

Answer 1

That's probably happening because the AFNetworking execute the callback very fast, for instance before the view of the view controller is loaded, maybe because you are using a local server or another configuration in viewDidLoad that is slow. In this case I would recommend to move the code to viewWillAppear or viewDidAppear since in that moment the view would be in the hierarchy and therefore you would be able to present another ViewController from there.

Answer 2

In my AFNetworking success callback I was setting some of the information obtained from the web server into NSUserDefaults. And then I was presenting the LoginViewController.
My AppDelegate was listening to NSUserDefaultsDidChangeNotification notification. The handler for this notification would set the launchViewController as the root view controller.
So, in the AFNetworking callback while I was asking LaunchViewController to present LoginViewController I was also sending off NSUserDefaultsDidChangeNotification which would cause the AppDelegate to load the LaunchViewController.
I never saw even a flicker of LoginViewController ever. So, I think the AppDelegate handler was getting fired first and then the presentLoginViewController was getting called. And this somehow lead to the views not being added to window hierarchy message.