UIViewControllerHierarchyInconsistency when trying to present a modal view controller

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

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:

Answer 2

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).