Question

I have a tab bar controller and inside it two controllers: a mapview controller and a tableview + NSFetcheddata controller. Both display info about a specific day from core data and have a button to display a day selector modally.

I have achieved having my controllers dataset changing when their modal view controller disappears through delegation but I would like the two controllers to update their data and not only the one who displayed the modal controller.

I thought about creating a protocol in both controllers and setting each other as its delegate but I would like to know if I’m doing right here.

Cheers,

Thierry

Answer 1

There are tons of different ways to do this. One way is to use NSNotificationCenter. Define your own custom notification name:

static NSString *const CSDataUpdatedNotification = @"CSDataUpdatedNotification";

Subscribe to this notification in both of your controllers:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(dataUpdated:) name:CSDataUpdatedNotification object:nil];

And implement dataUpdated: to update your data:

- (void)dataUpdated:(NSNotification *)notification
{
    // Handle updates here
}

In the controller causing the change, post the notification:

- (void)updateData
{
    // Data updating routine
    // ...

    [[NSNotificationCenter defaultCenter] postNotificationName:CSDataUpdatedNotification object:self];
}