CoreData 按 NSDate 排序不起作用？

Posted 2023-03-04

【中文标题】CoreData 按 NSDate 排序不起作用？

【英文标题】：CoreData Sort By NSDate not work?

【发布时间】：2011-09-13 08:54:32

【问题描述】：

在代码中：

- (NSFetchedResultsController *)getFetchedResultsController 
    if (_fetchedResultsController != nil) 
        return _fetchedResultsController;
    
    [NSFetchedResultsController deleteCacheWithName:@"LatestNews"];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:@"News" inManagedObjectContext:self.managedObjectContext]];
    [request setFetchLimit:kDefaultNewsLimit];
    [request setFetchBatchSize:20];
    [request setIncludesSubentities:NO];
    [request setIncludesPropertyValues:NO];
    NSSortDescriptor *dateSortor = [NSSortDescriptor sortDescriptorWithKey:@"dateAdded" ascending:NO];
    [request setSortDescriptors:[NSArray arrayWithObject:dateSortor]];

    _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"LatestNews"];
    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;


- (void)viewDidAppear:(BOOL)animated

    [super viewDidAppear:animated];
    if (isFirstLoading) 
        [refreshView refreshLastUpdatedDate];
        NSError *error;
        if (![self.fetchedResultsController performFetch:&error]) 
            if ([error code]) 
                NSLog(@"%@", [error localizedDescription]);
                exit(EXIT_FAILURE);
            
        
        loadMoreButton.hidden = self.numberOfLimitedNews > 0 ? NO : YES;
        [self.tableView performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:YES];

        [self.tableView setContentOffset:CGPointMake(0, -70) animated:YES];

        [refreshView setState:EGOOPullRefreshLoading];
        isRefreshing = YES;;
        [self performSelector:@selector(fetchNewsFromInternet) withObject:nil afterDelay:2];
        isFirstLoading = NO;
    

结果：

2011-09-13 16:48:20.959 HJNews[5971:bc03] 2011-02-04 06:00:00 +0000
2011-09-13 16:48:21.079 HJNews[5971:bc03] 2011-09-13 08:29:48 +0000
2011-09-13 16:48:21.230 HJNews[5971:bc03] 2011-02-19 01:30:00 +0000
2011-09-13 16:48:21.463 HJNews[5971:bc03] 2011-09-13 08:45:00 +0000
2011-09-13 16:48:21.879 HJNews[5971:bc03] 2011-03-06 02:00:00 +0000
2011-09-13 16:48:22.143 HJNews[5971:bc03] 2010-12-01 02:40:00 +0000
2011-09-13 16:48:22.229 HJNews[5971:bc03] 2011-09-13 02:03:43 +0000
2011-09-13 16:48:22.313 HJNews[5971:bc03] 2011-09-13 08:10:33 +0000
2011-09-13 16:48:22.446 HJNews[5971:bc03] 2011-01-02 06:00:00 +0000
2011-09-13 16:48:22.627 HJNews[5971:bc03] 2011-09-13 08:45:00 +0000
2011-09-13 16:48:22.978 HJNews[5971:bc03] 2011-01-23 02:00:01 +0000
2011-09-13 16:48:23.092 HJNews[5971:bc03] 2011-09-13 03:35:40 +0000
2011-09-13 16:48:23.196 HJNews[5971:bc03] 2011-02-18 06:20:00 +0000
2011-09-13 16:48:23.346 HJNews[5971:bc03] 2011-09-13 00:00:00 +0000
2011-09-13 16:48:23.812 HJNews[5971:bc03] 2011-02-08 06:00:00 +0000
2011-09-13 16:48:23.980 HJNews[5971:bc03] 2011-09-12 01:40:10 +0000
2011-09-13 16:48:24.179 HJNews[5971:bc03] 2011-01-18 06:00:00 +0000
2011-09-13 16:48:26.257 HJNews[5971:bc03] 2010-12-22 06:30:00 +0000
2011-09-13 16:48:27.783 HJNews[5971:bc03] 2011-02-08 06:00:00 +0000
2011-09-13 16:48:27.784 HJNews[5971:bc03] 2011-09-12 01:40:10 +0000
2011-09-13 16:48:27.785 HJNews[5971:bc03] 2011-01-18 06:00:00 +0000
2011-09-13 16:48:27.785 HJNews[5971:bc03] 2010-12-22 06:30:00 +0000
2011-09-13 16:48:27.786 HJNews[5971:bc03] 2011-09-13 02:10:17 +0000

我不知道为什么它不起作用，我似乎是随机排序的……有人帮我吗？

第一次加载正常，点击加载更多按钮或更改（category navigation bar）时异常

【问题讨论】：

什么是添加日期？是 NSDate 吗？

是的。是服务器数据库时间添加的消息。

嗯。您能否向我们展示获取获取结果并写出上述诊断信息的代码？

尝试删除缓存。将缓存名称设置为 nil。

我删除了缓存，但问题没有解决...

【参考方案1】：

再次检查您的数据模型中dateAdded 的属性类型是否设置为Date，在您的类文件中设置为NSDate。

【讨论】：

是的，我查过了，它们是 NSDate 类型；-(

检查您的输出不是来自NSSet（未排序），而是来自NSArray（已排序）。

我查找了 NSFetchedResultsController 的 fetchedObjects 类型，它是 _PFMutableProxyArray，但是当我更改谓词时（单击导航类别的顶部，请参阅image），它更改为 _PFArray

第一次加载正常，点击加载更多按钮或更改（分类导航栏）时异常