ios – NSFetchedResultsController始终不返回任何行

我试图让NSFetchedResultsController使用我的tableview,但尽管我尽最大努力正确设置它,它总是返回没有行.我通过Finder打开了我的数据存储,并通过sqlite编辑器验证了实际上有很多记录,但它总是返回零.我错过了什么？

控制器的自定义吸气器：

- (NSFetchedResultsController *)fetchedResultsController {
    if (fetchedResultsController_ != nil) {
        return fetchedResultsController_;
    }

    RBGameItemController* itemController = [RBGameItemController sharedInstance];

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"GameItem" inManagedobjectContext:itemController.managedobjectContext];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

    [fetchRequest setFetchBatchSize:20];

    NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest  
                                                                                                  managedobjectContext:itemController.managedobjectContext 
                                                                                                    sectionNameKeyPath:nil 
                                                                                                             cacheName:@"Root"];
    self.fetchedResultsController = theFetchedResultsController;
    self.fetchedResultsController.delegate = self;

    [sort release];
    [fetchRequest release];
    [theFetchedResultsController release];

    return self.fetchedResultsController;
}

我在viewDidLoad中获取数据：

- (void)viewDidLoad {
    [super viewDidLoad];

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

获取结果代表：

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller is about to start sending change notifications,so prepare the table view for updates.
    [self.tableView beginUpdates];

    NSLog(@"controllerWillChangeContent");
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
    NSLog(@"controller:didChangeObject:");
    UITableView *tableView = self.tableView;

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[self.tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            // Reloading the section inserts a new row and ensures that titles are updated appropriately.
            [tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
    NSLog(@"controller:didChangeSection:");
    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    NSLog(@"controllerDidChangeContent:");
    // The fetch controller has sent all current change notifications,so tell the table view to process all updates.
    [self.tableView endUpdates];
}

我正在实现section和row number的两种方法,它们为section返回1,为行返回0：

- (NSInteger) numberOfSectionsInTableView:(UITableView *)tableView {
    int sections = [[self.fetchedResultsController sections] count];
    NSLog(@"sections=%i",sections);
     return sections;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    id<NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    int rows = [sectionInfo numberOfObjects];

    NSLog(@"rows=%i",rows);

    return rows;
}

NSArray *entities = [itemController.managedobjectContext executeFetchRequest:fetchRequest error:&error];
NSLog(@"%d",entities.count);