iPhone - calling a method in parent view controller

Question

Hi, have hunted around for an answer to this one, but can't seem to find a definitive solution - hoping someone can help here!

I'm building a multiview app for the iPhone. I've created a UIViewController called "MainViewController", which loads in other views as required. There's quite a lot of navigation between screens, so what I'd like to do is have a "ViewSwitcher" method in MainViewController that the child view controllers can call to ask for the view to switch away to another child view.

How can I call the "ViewSwitcher" method from the child controllers? I've managed to achieve this at present by creating an UIView *"parent" property in each child view controller, and populating this on first loading the child view. I can then call the method using [parent ViewSwitcher]. This seems a bit clunky, and I'm concerned I'm creating some horribly recursive structure. Is there a better way?

Thanks in advance.

Answer 1

You could create a singleton object. This cocoawithlove article does a magnificent job on this topic.

Answer 2

Here's something that looks clunky, but it should demonstrate the general idea:

NSArray *viewControllerArray = [self.navigationController viewControllers];
int parentViewControllerIndex = [viewControllerArray count] - 2;
[[viewControllerArray objectAtIndex:parentViewControllerIndex] setBackBarButtonItemTitle:@"New Title"];

Much of this can easily be replaced with a #define macro:

#define CurrentParentViewController [[self.navigationController viewControllers] objectAtIndex:[[self.navigationController viewControllers] count] - 2]

You might then use it as follows:

[CurrentParentViewController setBackBarButtonItemTitle:@"New Title"];

This would obviously crash and burn if you call this at the bottom-most view controller in the navigation stack, but presumably you would know when you're using this approach. You could, for example, call [[self.navigationController viewControllers] count] to make sure you can run this.