How to share a ManagedObjectContext when using UITabBarController

Question

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

Answer 1

Hello I know this is an old thread, but I'm also having problems finding the best way to handle sharing a MOC between TABS - wish Marcus Zarra's link on the subject was still active. Marcus totally rocks, makes data cool.

This is my current solution in application didFinishLaunching:

NSArray *viewControllers = [tabBarController viewControllers];
    NSManagedObjectContext *context = self.managedObjectContext;
    for (id viewController in viewControllers) {
        [viewController setManagedObjectContext:context];

}

Answer 2

I've ran into this same problem, i'll share my solution.

First you need a reference to the Nav Controller in the Tab Bar in the nib file, make sure you connect it up.

IBOutlet UINavigationController *navigationController;

Then, get the Controller as recommended in the support docs and send it the managedObjectContext:

SavedTableViewController *saved = (SavedTableViewController *)[navigationController topViewController];
saved.managedObjectContext = self.managedObjectContext;

Alex (from another post) is right, "You should generally stay away from getting shared objects from the app delegate. It makes it behave too much like a global variable, and that has a whole mess of problems associated with it."

Answer 3

If you want to use the dependency injection method to pass the managed object context with a tab bar controller, a more robust solution would be to loop on all the view controllers in applicationDidFinishLaunching:

for (id vc in tabBarController.viewControllers) {
    [vc setManagedObjectContext:self.managedObjectContext];
}