I have an iPhone application that has a MainWindow.xib holding a UITabBarController, which in turn has a UINavigationController and a custom UIViewController subclass in its ViewControllers array. The root view controller for the UINavigationController and the custom view controller are both loaded from other xib files.
The app uses core data, the stack is initialized in the app delegate (as per the convention).
The app delegate adds the UITabBarController to the window:
- (void)applicationDidFinishLaunching:(UIApplication *)application {
// Configure and show the window
[window addSubview:[tabBarController view]];
[window makeKeyAndVisible];
}
I realize that I need to propagate a pointer to the ManagedObjectContext created in the app delegate, but I don't know how to proceed (even reading all the good commentary on the topic here and here):
I guess I don't understand well enough how to work with the UITabBarController.
Ideally you want to pass either the NSManagedObjectContext
, NSFetchedResultsController
or the relevant NSManagedObject
"down" into the UIViewController
. This allows the "parent" to control the "child" and determine what the child should have. This creates a more loosely coupled design and allows you to easily re-arrange UIViewController
instances as needed. It also makes it easier to reuse a UIViewController
.
In a tab view design it is no different. Your AppDelegate passes the NSManagedObjectContext
to whoever is responsible for creating the initial UIViewController
instances that go into the UITabBarController
. In turn that creator passes the relevant information (NSManagedObject
, NSFetchedResultsController
, and/or NSManagedObject
instances) into the UIViewController
instances as it is constructing them.