referencing an instantiated object in another class in objective C

Question

I am working in xcode on an ipod app in objective C, and I have a field (navigationController) in one of my classes (rootViewController). How do I reference the instantiated rootViewController's navigationController from another class? For example, how would I do this if I want to reference the navigationController from the FirstViewController.m class?

I seem to only be able to find references for this to reference the application delegate.

If I want to reference the application delegate with FirstViewController, I just say:

MyAppDelegate *delegate = [[UIApplication sharedApplication] delegate];

[delegate.navigationController pushViewController:childController animated:YES];

how do I do this for the rootViewController class instead of MyAppDelegate?

Answer 1

Based on the question you are asking, it seems that you want to call methods on the UINavigationController that is higher up in the stack. All UIViewControllers already have a property of navigationController which is the UINavigationController that is an ancestor to this ViewController on the stack.

So if you had a RootViewController, called root, that at some point did this

FirstViewController * first = [[FirstViewController alloc] initWithNibName:@"FirstView" bundle:nil];
[self.navigationController pushViewController:first animated:YES];
[first release];

Then first.navigationController == root.navigationController

So inside of first calling [self navigationController] will give you the same navigationController that first was pushed onto in the first place.

Answer 2

One object needs a reference to the other. There are many ways to make this happen. For example:

• Have the same object create both and, since it knows them both, tell them about each other
• Create them in the same nib and hook them up with normal connections
• Have the owner of the nib one of the objects is in know about the other

Essentially, this is just a matter of designing your application properly so that the objects can be told about each other. There is no one magic thing you do.