Question

我有由fetched results controller管理的表视图。我想要的是，当用户点击分段控件时更改排序顺序。这就是我创建获取结果控制器的方法：

- (NSFetchedResultsController *)frc {

    if (_frc != nil) {
        return _frc;
    }

    NSString *sortCase;
    switch (self.sortOrder) {
        case tableSortServer:
            sortCase = [NSString stringWithFormat:@"%@", CD_SORT];
            break;

        case tableSortDate:
            sortCase = [NSString stringWithFormat:@"%@", CD_DATE];
            break;

        default:
            sortCase = [NSString stringWithFormat:@"%@", CD_SORT];
            break;
    }


    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription
                                   entityForName:CD_ENTITY_NAME  inManagedObjectContext:self.getManagedObjectContext];
    [fetchRequest setEntity:entity];

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

    [fetchRequest setFetchBatchSize:BATCH_SIZE];

    NSFetchedResultsController *theFetchedResultsController =
    [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                        managedObjectContext:self.getManagedObjectContext sectionNameKeyPath:nil
                                                   cacheName:@"Root"];
    self.frc = theFetchedResultsController;
    _frc.delegate = self;

    return _frc;

}

在分段控制器回调方法中，我做了：

- (IBAction)sortOrderChanged:(id)sender {

    UISegmentedControl *sc = sender;
    if (sc.selectedSegmentIndex == 0){
        self.sortOrder = tableSortServer;
        [self.tableView reloadData];
    }    else {
        self.sortOrder = tableSortDate;
        [self.tableView reloadData];
    }

}

然而，它不起作用。如何实现这一任务？（重新加载具有不同排序顺序的表）？

Answer 1

也许这是因为

if (_frc != nil) {
    return _frc;
}

你重装表。它使用旧的获取结果控制器。因此，您的self.sortOrder = tableSortServer不会被考虑在内。我认为每次重新加载表视图之前都需要设置新的排序描述符（并实际执行获取）

重新加载fetchedResultsController数据

1 个答案: