UIViewController -viewDidLoad not being called.

Question

As a Cocoa noob, I'm having a few issues with Interface Builder, UIViewController and friends.

I have a UIViewController subclass with a UIView defined in a xib, and with the controller's view outlet connected to the view. The xib's "file's owner" is set as my controller subclass.

In this one instance, the following code to load the controller/view (from the main view controller) doesn't work as expected:

if ( self.myViewController == nil )
{
 self.myViewController = [[MyViewController alloc]
      initWithNibName:@"MyViewController" bundle:nil];
}


[self.navigationController pushViewController:self.myViewController animated:YES];

In MyViewController's methods, I have placed breakpoints and log messages to see what is going on:

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
         NSLog(@"initWithNibName\n");
    }

   return self;
}

- (void)viewDidLoad 
{
    [super viewDidLoad];
    NSLog(@"viewDidLoad\n");
}

My expect result is:

Both -initWithNibName and -viewDidLoad methods are called, and myViewController's view is displayed.

Observed result:

Only -initWithNibName is called, the view is not displayed.

Have I missed something? Can anyone recommend anything to check? (Particularly in the wondrously opaque Interface Builder tool).

Answer 1

make sure that the view outlet in File's Owner (your viewController subclass) is connected to the actual view (i.e. the 480X320 canvas you see on your screen that you use to build your UI)

Answer 2

It looks like a capitalization problem to me. You're referencing the class MyViewController instead of the property myViewController in the call to pushViewController.

Answer 3

Check your run log for errors. Almost certainly, the NIB is not loading, and there should be an error to that effect. The most likely cause for that is failure to put it in the bundle. Look in your "Copy Resources" build phase and make sure that the XIB is actually being copied. Build for the simulator, and go down into the build directory and make sure that the NIB is in the .app bundle.

Answer 4

Ok, I have a partial answer - maybe the gurus can explain some more. The problem is:

[self.navigationController pushViewController:myViewController animated:YES];

Looking more closely, in this case self.navigationController is nil - so the push message is going no-where.

Instead, if I send:

[self.view addSubview:self.myViewController.view];

Then the view appears and -viewDidLoad is called.

I'm not entirely sure why self.navigationController is not set in this instance - the only thing I can think of is that self is a subclass of UIViewController rather than UITableViewController (where the pushViewController code came from).

Also, silently allowing messages to go to nil seems like a bad idea, although these answers say otherwise. See also my question here.

Final edit:

Answers in comments below, I've realised the display function that I was actually after (given myViewController is modal) is:

[self presentModalViewController:myViewController animated:YES];

Thanks everyone for their helpful responses.

Answer 5

SOLUTION FOUND!!!!!

Even something as innocuous as this makes the viewDidLoad method call happen.

Insert this right after alloc initwithnibname

viewController.view.hidden = NO; //calls viewDidLoad

Answer 6

RE: SOLUTION FOUND!!!!!

Indeed that seems to be a working solution, however the real trick is not in setting the view.hidden property to NO, what makes the view load from the nib file is the calling of the UIViewController's view method, the view only actually gets loaded from the nib when the view method is called for the first time.

In that sense, a simple [viewController view] message would force the view to load from the nib file.