UIViewControllerHierarchyInconsistency when trying

Question

Trying to present a modal view controller with the following code

MapViewController *mapView = [[MapViewController alloc] initWithNibName:@"MapViewController" bundle:nil];
    mapView.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self.navigationController presentModalViewController:mapView animated:YES];
    [mapView release];

Keep getting the following error..

'UIViewControllerHierarchyInconsistency', reason: 'A view can only be associated with at most one view controller at a time! View <UIView: 0x1ed815a0; frame = (0 20; 320 460); autoresize = W+H; layer = <CALayer: 0x1ed81600>> is associated with <UIViewController: 0x1ed835a0>. Clear this association before associating this view with <MapViewController: 0x1dd947c0>.'

This is an old project that I havent touched in months, wonder what could cause such an error?

Answer 1

I had this problem when my Nib had a UIViewController in the file at top level. So loading from Nib created that UIViewController, then I tried to use it from my class, which was in the position of MapViewController in your code.

In my case the solution was simply to remove the UIViewController from my Nib file.

Answer 2

You should do it like this..

MapViewController *mapView = [[MapViewController alloc] initWithNibName:@"MapViewController" bundle:nil];
UINavigationController *navCntrlr = [[UINavigationController alloc] initWithRootViewController:mapView];
mapView.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
//hide navigation bar if needed
[self.navigationController presentModalViewController:navCntrlr animated:YES];
[mapView release];

Answer 3

I had this problem when running Apple's example audio app MixerHost on the iOS 6 simulator.

The equivalent of the above fix, namely to edit the supplied MixerHostViewController.xib by dragging the View object to the top level, and discarding the now-empty ViewController that used to contain it, worked perfectly (though not before I'd spent hours working out what the underlying problem was, so I'm feeling done-over by Apple at the moment - seems they tightened something up but didn't bother to check if it broke their sample apps).

Answer 4

Maybe in some cases it is better to take another approach and not delete the UIViewController from the NIB, because, for one thing, by removing the view controller from the NIB's hierarchy, you lose the Auto Layout margins.

Why not just leave the UIViewController in your nib (.xib) and create an outlet for it in the file owner class? Then, rather than instantiate the view controller directly in you code, load the nib with the UINib class, and, at the optimal time (from the memory/resource usage standpoint), invoke the nib instance's instantiateWithOwner() method to unarchive NIB and connect the nib objects to the owner class's outlets.

    @IBOutlet var myViewController: myViewController?

    var nib : UINib?
    nib = UINib(nibName: "TheNib", bundle: nil)
    if (nib == nil) {
        println("could not load nib: TheNib.xib")
    }
    nib!.instantiateWithOwner(self, options: nil)

Answer 5

This happened to me already twice in the newest Xcode release. In both cases I needed to make changes to the UIViewController's XIB file (In you case it would be MapViewController.xib:

BEFORE:

1. Move main View out of View Controller's children:
2. Remove View Controller from the XIB (it is not necessary since File's Owner should be of its Class already):

AFTER: