CoreData MergeChange

// this is called from mergeChanges: method,
// requested to be made on the main thread so we can update our table with our new earthquake objects
//
- (void)updateContext:(NSNotification *)notification
{
    NSManagedObjectContext *mainContext = [self managedObjectContext];
    [mainContext mergeChangesFromContextDidSaveNotification:notification];
     
    // keep our number of earthquakes to a manageable level, remove earthquakes older than 2 weeks
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Earthquake"
                                              inManagedObjectContext:managedObjectContext];
    [fetchRequest setEntity:entity];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"date < %@", self.twoWeeksAgo];
    [fetchRequest setPredicate:predicate];
    
    NSError *error = nil;
    NSArray *olderEarthquakes = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
    
    Earthquake *earthquake;
    for (earthquake in olderEarthquakes) {
        [self.managedObjectContext deleteObject:earthquake];
    }
    
    // update our fetched results after the merge
    //
    if (![self.fetchedResultsController performFetch:&error]) {
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate.
        // You should not use this function in a shipping application, although it may be useful
        // during development. If it is not possible to recover from the error, display an alert
        // panel that instructs the user to quit the application by pressing the Home button.
        //
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    
    [fetchRequest release];
    [self.tableView reloadData];
}