Question

I have a app with TabBar, under the main tabbar there are navigation controllers, under these there are ‘branches’ of tableviewcontollers.

How can I make two unrelated, non segue-connected, under two different tab icons viewcontrollers exchange information between them?

Tried with delegating but I can’t get the instance variable to the delegator from the delegatee (there’s no relation between them, no segue.destinationviewcontroller etc)

any ideas?

practical:
the app shows list of subitems (the parent tableview has the items), andon the other tab the recent items that were selected are getting added (but maxiumum 10 and sorted by most recent).. been breaking my ** on it…

thanks

Answer 1

Have you considered posting an NSNotification, passing the data you want to transfer in userInfo?

From the Apple documentation:

The object sending (or posting) the notification doesn’t have to know
what those observers are. Notification is thus a powerful mechanism
for attaining coordination and cohesion in a program. It reduces the
need for strong dependencies between objects in a program (such
dependencies would reduce the reusability of those objects).

The class sending a notification does it as follows:

[[NSNotificationCenter defaultCenter] postNotificationName: <notification-name> 
                                                    object: self
                                                  userInfo: <your-user-info>]; 

and the class listening for the notification registers for notifications using:

[[NSNotificationCenter defaultCenter] addObserver: self 
                                         selector: @selector(someMethod:) 
                                             name: <notification-name> 
                                           object: nil];

and has a method:

- (void) someMethod: (NSNotification *) notification
{
    NSDictionary * myInfo = notification.userInfo;

    //do something with myInfo
}