相关疑难解决方法(0)

我在NSFetchedResultsController和iOS 5中提供的新NSOrderedSet关系中遇到了一个问题(理解问题).

我有以下数据模型(好吧,我的真实的不是抽屉和袜子!)但这只是一个简单的例子:

Drawer和Sock都是Core Data模型/商店中的NSManagedObjects.上Drawer的socks关系是一个有序的一对多关系Sock.想法是袜子按特定顺序放在抽屉里.上Sock的drawer关系是逆socks关系.

在UIViewController中,我正在基于这些实体绘制UITableView.我正在用桌子喂餐桌NSFetchedResultsController.

- (NSFetchedResultsController *)fetchedResultsController1 {
    if (_fetchedResultsController1 != nil) {
        return _fetchedResultsController1;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Sock" inManagedObjectContext:[NSManagedObjectContext MR_defaultContext]];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"drawer.socks" ascending:YES];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

    self.fetchedResultsController1 = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[NSManagedObjectContext MR_defaultContext] sectionNameKeyPath:nil cacheName:@"SocksCache"];
    self.fetchedResultsController1.delegate = self;

    return _fetchedResultsController1;    
}

当我运行它时,我得到以下错误: *** Terminating app due to …