ios – 实体商店不是键值“category.name”的键值编码兼容

我有这两个实体：

店

类别

我正在尝试从Shop实体访问category.name但是我收到一个错误：

- (void)updateDetails:(NsmanagedObject *)shop
{
    NSLog(@"updateDetails: %@",shop);

    if (shop == nil)
        return;

    self.nameLabel.text =      [[shop valueForKey:@"name"] description];
    self.categoryLabel.text =  [[shop valueForKey:@"category.name"] description];
    self.addressLabel.text =   [[shop valueForKey:@"address"] description];
    self.telephoneLabel.text = [[shop valueForKey:@"telephone"] description];

    NSnumberFormatter* f = [[NSnumberFormatter alloc] init];
    [f setnumberStyle:NSnumberFormatterdecimalStyle];
    NSnumber* acceptRate = [f numberFromString:[[shop valueForKey:@"acceptRate"] description]];

    _ratingControl.rating = [acceptRate unsignedIntValue];
}

我通过这种方式检索Shop实体：

NsmanagedObjectContext *context = [self managedObjectContext];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Shop"
                                          inManagedObjectContext:context];

NSFetchrequest *fetchrequest = [[NSFetchrequest alloc] init];
[fetchrequest setEntity:entity];

NSArray *results = [context executeFetchrequest:fetchrequest error:nil];

但我得到这个错误：

‘[< NsmanagedObject 0x1cdb4890> valueForUndefinedKey：]：实体Shop不是键值“category.name”的键值编码兼容.

我该如何解决这个错误？