Send NSNotification from classA to classB

So i have an app with an In App purchase. The In App purchase is managed in FirstViewController. When the user has purchased the product, i want to send out a Notification to my MainTableViewController to reload the tables data and show the new objects that were purchased in the In App purchase. So basically i want to send a notification from class A to class B and class B reloads the data of the tableview then. I have tried using NSNotificationCenter, but with no success, b开发者_JAVA百科ut i know that its possible with NSNotificationCenter i just don't know how.

In class A : post the notification

[[NSNotificationCenter defaultCenter] postNotificationName:@"DataUpdated"
                                                        object:self];

In class B : register first for the notification, and write a method to handle it.
You give the corresponding selector to the method.

// view did load
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(handleUpdatedData:)
                                             name:@"DataUpdated"
                                           object:nil];

-(void)handleUpdatedData:(NSNotification *)notification {
    NSLog(@"recieved");
    [self.tableView reloadData];
}

Ok I'm adding a little bit more information to vince's answer

In class A : post the notification

[[NSNotificationCenter defaultCenter] postNotificationName:@"DataUpdated"
                                                   object:arrayOfPurchasedObjects];

In class B : register first for the notification, and write a method to handle it.
You give the corresponding selector to the method. Make sure your class B is allocated before you post the notification otherwie notification will not work.

- (void) viewDidLoad {
// view did load
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(handleUpdatedData:)
                                             name:@"DataUpdated"
                                           object:nil];
}

-(void)handleUpdatedData:(NSNotification *)notification {
    NSLog(@"recieved");
    NSArray *purchased = [notification object];
    [classBTableDataSourceArray addObjectsFromArray:purchased];
    [self.tableView reloadData];
}

- (void) dealloc {
    // view did load
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                 name:@"DataUpdated"
                                               object:nil];
    [super dealloc];
 }

Maybe you trying to send notification from another thread? NSNotification won't be delivered to the observer from another thread.