iphone - NSFetchResultsController 委托(delegate)没有被调用

Question

我有以下代码:

- (NSFetchedResultsController *)fetchedResultsController {
    // Set up the fetched results controller if needed.
    if (fetchedResultsController == nil) {

 NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        // Edit the entity name as appropriate.
        NSEntityDescription *entity = [NSEntityDescription entityForName:@"DiskStory" inManagedObjectContext:self.managedObjectContext];
        [fetchRequest setEntity:entity];

        fetchRequest.predicate = [NSPredicate predicateWithFormat:@"isRemoved == %@", [NSNumber numberWithBool:NO]];

        // Edit the sort key as appropriate.
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"created" ascending:NO];
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

        [fetchRequest setSortDescriptors:sortDescriptors];

        // Set limit
        [fetchRequest setFetchBatchSize:25];
        // Set batch size
        [fetchRequest setFetchLimit:50];


        NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:kSavedStoryCache];
        aFetchedResultsController.delegate = self;
        fetchedResultsController = aFetchedResultsController;
 }
    return fetchedResultsController;
}    

在我看来DidLoad 我有:

 NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }

我想知道为什么我的:

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {

}

代表，不是叫吗？我在里面放了一个断点。任何的想法？

Answer 1

我之前也遇到过这个问题，调用时没有调用performFetch第一次，但仅限于 fetchedResultsController 中的数据实际上是改变了。例如，当您从此获取结果中的上下文中删除对象时，将调用委托(delegate)。