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iosnibnulliboutlet

UIView in nib is nil on iPad, and not nil on iPhone

I have a weird problem with my app. I load a VC at runtime with a NIB named "LoginViewController." That NIB has a bunch of outlets to UIView objects that are placed in the NIB like so:

enter image description here

At runtime I dynamically place those UIView objects as headers in my table view. Each separate UIView in this case (except for the one with the UITableView in it, on the right) is set as an IBOutlet like so. Each has a different name of course:

@property (strong, nonatomic) IBOutlet UIView *connectionInProgressView;

Now, in my VC's viewDidLoad method I run through all four of these separate views and ensure they exist by writing to the log:

NSLog(@"connection in progress view: %@", self.connectionInProgressView);

My problem is this: self.connectionInProgressView is nil on iPad and not nil on iPhone. All the other views regardless of platform are NOT nil and are instantiated. I'm running this in the simulator on iOS 5.0, 5.1 and 6.1. I can recreate the issue on all iPad simulators. My app works just fine and loads the view with the spinner on iPhone, but on iPad it can't load that view because it's nil! Why!?

I have tried the following:

  • Checking that my NIB's File's Owner points to the proper view
  • That the self.connectionInProgressView doesn't point to any other IBOutlet
  • Checking that all the other sub views are hooked up the same way as the offending view. They are.
  • Deleting self.connectionInProgressView and re-creating it after removing all its NIB connections.
  • Removing the activity indicator from the view and loading just a view with a UILabel inside. No luck, its not the activity indicator.
  • Checked for any code in the VC that might reference self.connectionInProgressView. There is none (other than it's nil statement in viewDidUnLoad).
  • Checking the property attribute types on my AppDelegate properties of the UINavigationController and LoginViewController.
  • Retaining a copy of LoginViewController on AppDelegate, though this seems wasteful and didn't make a difference in the outcome.

[EDIT 2]

Question: How is the VC loaded

I have a UINavigationController that is a property on my AppDelegate. That UINavigationController is alloc-init'd in applicationDidFinishLaunchingWithOptions to which I pass my VC as a root view controller. I instantiate the VC at this point.

// Create login/start up views
LoginViewController *loginViewController = [[LoginViewController alloc] initWithNibName:@"LoginViewController" bundle:nil];

self.loginViewNavigationController = [[UINavigationController alloc] initWithRootViewController:loginViewController];

if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
    self.loginViewNavigationController.modalPresentationStyle = UIModalPresentationFormSheet;

Note that this is working on iPhone even though I'll present this UINavigationController later as a modal form sheet (not sure if that is contributing to my issue) on iPad.

Some time later in AppDelegate when a different delegate class throws an event I will present this UINavigationController, with my VC in it modally. I do that like this:

if (self.loginViewNavigationController != nil) {

    [self.window.rootViewController presentViewController:self.loginViewNavigationController animated:YES completion:nil];
}

I'm going bonkers trying to determine why this one particular view dragged onto my NIB and wired up the same as all the others is nil on an iPad and not nil on iPhone.

[EDIT 1] While searching for a duplicate question I failed to find this:

A few IBOutlets pointing to nil

I am not alone!

Any ideas?

Solution

  • As you are building an Universal app, are you sure you didn't create a separate NIB for iPhone and iPad (LoginViewController.xib and LoginViewController~ipad.xib typically)?

    Or maybe you thought you have only one XIB but at some point you had a dedicated XIB for iPad that got compiled into a NIB and even if you deleted the XIB file in your project, the compiled NIB dedicated for iPad is still in the build products.

    In any case, try to:

    • Clean your project, or even better, your Build Products Directory
    • To do the latter, you can delete your Derived Data folder ("Organizer" window -> "Projects" tab -> Select your project on the left -> click on the "Delete" button next to "Derived Data")
    • Delete your app from all your Simulators, just to be sure
    • Build and Run again

    If this does not work, some ideas to help you debug and identify if the issue is related to the iPad using a different XIB or not:

    • You can try some tests like modifying another IBOutlet of your XIB, for example disconnect one of the other IBOutlet that are not nil from the view it was connected to in the XIB, so that when you run your app again it should be logged as nil this time. If it is nil on the iPhone Simulator (as expected as you just disconnected it)… but still non-nil on the iPad Simulator, then it will definitely mean that you use a different XIB file for iPhone and iPad.
    • You can also change in the XIB the color of our of your UIView that is correctly connected to one of your IBOutlet, and see if the change is reflected in both iPhone and iPad or only on iPhone, so check that this XIB you are editing is the same used in iPad or not.