R – When do I not need to specify File’s Owner for a nib

That's correct. The File's Owner for a Nib file is the entry point into that nib. Since nothing outside your nib can refer to anything but the File's Owner, only the File's Owner can refer to other top-level items in the nib. If the File's Owner doesn't refer to them, then there is no way to release those objects when the nib is no longer needed, and they will hang around in memory.

The life cycle of a nib is something like this:

1. The nib is loaded and the File's Owner is associated with an object you specified.
2. Memory is allocated for all the top-level objects in the nib.
3. All the outlets are hooked up as specified in the nib.
4. ... stuff happens ...
5. The File's Owner object is sent a release message.
6. The File's Owner releases all the objects hooked up to its outlets.

As you can see, any object that was allocated in the second step will still be floating around in memory if it wasn't released in the final step.

I think you might not be understanding how the File's Owner is meant to be used in a NIB file. I've written up a response describing the file's owner under another question.

When you invoke this line:

[[MyNavCtrlrSubClass alloc] initWithNibName:@"MenuController" bundle:nil]

You create an instance of MyNavCtrlrSubClass, and tell it to load @"MenuController". Then in the MenuController.xib file, there is a second unrelated UINavigationController with things inside of it. When MenuController.nib is loaded at runtime, that second navigation controller will be created.

A second problem is that telling a UINavigationController to load a NIB file isn't really sensible because navigation controllers create and manage their own views. You really want to create the root view controller, and tell that view controller to load a NIB file.

Try this:

MyRootViewController *rootController = [[[MyRootViewController alloc] initWithNibName:@"AnotherViewController" bundle:nil] autorelease];
MyNavCtrlrSubClass *menu = [[MyNavCtrlrSubClass alloc] initWithRootViewController:rootController];

Where your XIB File looks like this:

• File's Owner (Class set to MyRootViewController, view outlet connected to subsequent UIView)
• UIView
  • Subview A
  • Subview B

After you're confortable with how all of this is working, you might also consider instantiating the navigation controller and root view controller in one XIB file like you were starting to do in the code you posted.