对支持 CoreData 的 NSArrayController 进行排序时遇到问题

Question

我试图从我的 Core Data 支持的 NSArrayController 中检索排序对象数组。一旦 ManagedObjectContext 准备就绪，我会触发一个通知，拥有 NSArrayController 的对象会监听该通知，然后使用 sortDescriptors 设置获取请求。但是，数据永远不会排序。我已经为此苦苦思考了好几个小时了。

我得到了数组中的预期数据，但它根本没有排序。有人知道我哪里出错了吗？

// Elsewhere in code
...
_charts = [[NSArrayController alloc] init];
_charts.entityName = @"Charts";
...

// When Cored Data and Managed Object Context is ready
-(void)mangagedObjectContextReady
{
    NSManagedObjectContext *moc = ((AppDelegate *)[NSApp delegate]).managedObjectContext;
    _charts.managedObjectContext = moc;
    _charts.usesLazyFetching = NO;
    _charts.automaticallyPreparesContent = YES;
    _charts.automaticallyRearrangesObjects = YES;

    // Create fetch request for data
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    fetchRequest.entity = [NSEntityDescription entityForName:@"Charts" inManagedObjectContext:moc];

    // Create the sort descriptors for the Charts entity
    // Name and chartType are properties on the entity "Charts"
    NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(caseInsensitiveCompare:)];
    NSSortDescriptor *chartTypeDescriptor = [[NSSortDescriptor alloc] initWithKey:@"chartType" ascending:YES selector:@selector(caseInsensitiveCompare:)];
    fetchRequest.sortDescriptors = @[nameDescriptor, chartTypeDescriptor];

    NSError *error = nil;
    BOOL success = [_charts fetchWithRequest:fetchRequest merge:NO error:&error];
    if(!success)
        NSLog(@"Error %@:", [error localizedDescription]);
    else {
       [_charts rearrangeObjects];
       [_tv reloadData];
    }

我使用这个方法来获取一个数组或排序的对象..但是数据没有按照上面的排序描述符排序？

[_charts.arrangedObjects objectAtIndex:row]

Answer 1

_charts.sortDescriptors = @[nameDescriptor, chartTypeDescriptor];