Accessing a MKMapView through the tab bar

Question

I have a tabbar application and on the first tab I have a MKMapView. What I want to do is from somewhere else in the application, switch the active tab to the mapview and set the mapview's region based on the data in the previous view (the one with the button to switch to the mapview).

What I've tried is:

[self.tabBarController setSelectedView:0];
UIMapViewController *mapView = [self.tabBarController.viewControllers objectAtIndex:0];
[mapView displayBookmarkAnnotation:bookmark];

This just causes the app to crash unable to find the method I created. I don't think I've chosen the best path to implement this but I'm really not sure how I should go about it.

[Update] Casting the controller returned by the tabBarController had no effect.

[Solved] I was trying to cast a UINavigationController to my mapView

[self.tabBarController setSelectedView:0];
UINavigationController *navController = [self.tabBarController.viewControllers objectAtIndex:0];
//if the tab has other views open, return to mapView
[navController popToRootViewControllerAnimated:YES];
UIMapViewController *mapView = (UIMapViewController *)[navController visibleViewController];
[mapView customMessage:object];

Answer 1

What you want to do is create a subclass or a category of the UITabBarController that

1. registers for NotificationCenter events that you define
2. handles the events with a new selector. I generally use do/did naming convention for them.

When the event comes through you set the selectedIndex.

Answer 2

Why not route it through your AppDelegate? The AppDelegate can have a UITabBarController and the MKMapView (both wired through interface builder.) The UIButton handler would then also be in the AppDelegate so that it can call -[UITabBarController setSelectedView:] and -[MKMapView setRegion:].

Answer 3

Are you sure the main view controller for that tab is not a UINavigationController? If so, you can get the root view controller for that which should be your UIMapViewController.

It would be good to put a direct reference in the AppDelegate though if you are going to be calling it from elsewhere.