NSFetchedResultsController组每4小时分成几个部分-Java 学习之路

我正在尝试将一系列NSManagedObjects分组 . 每个部分代表一天内4小时的时间段 .

- (NSString *)sectionIdentifier
{
    // Create and cache the section identifier on demand.

    [self willAccessValueForKey:@"sectionIdentifier"];
    NSString *tmp = [self primitiveSectionIdentifier];
    [self didAccessValueForKey:@"sectionIdentifier"];

    if (!tmp)
    {
        NSCalendar *calendar = [NSCalendar currentCalendar];
        NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit) fromDate:[self created]];
        tmp = [NSString stringWithFormat:@"%.0f %d %d %d", round(components.hour % 4), components.day, components.month, components.year];
        [self setPrimitiveSectionIdentifier:tmp];
    }
    return tmp;
}

在上面的代码中，在NSManagedObject中找到，瞬态属性 sectionIdentifier 返回一个字符串，该字符串包含它所处的周期（4小时），创建它的日期，月份和年份 .

但是，尽管NSFetchedResultController的fetchRequest的排序描述符设置为按创建日期的顺序对结果进行排序（最新的对象位于底部，最旧的位于顶部），但由于节标识符未正确排序，提取请求失败 .

- (NSFetchedResultsController *) fetchedResultsController {
    if (!_fetchedResultsController) {
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        [fetchRequest setEntity:[NSEntityDescription entityForName:@"PSSpace" inManagedObjectContext:self.managedObjectContext]];
        [fetchRequest setSortDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"created" ascending:YES]]];
        _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:@"sectionIdentifier" cacheName:nil];
        [_fetchedResultsController setDelegate:self];
    }
    return _fetchedResultsController;
}

CoreData：error：（NSFetchedResultsController）索引10处的获取对象具有乱序部分名称'1 14 12 2013.对象必须按部分名称排序'

请告诉我如何通过订购解决这个问题？

谢谢 .

1 回答

尝试类似的东西

if (!tmp) {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit) fromDate:[self created]];

    NSUInteger _y = (components.year * 1000000);
    NSUInteger _m = (components.month * 10000);
    NSUInteger _d = (components.day * 100);
    NSUInteger _h = round(components.hour / 4);

    NSUInteger token = (_y + _m + _d + _h);

    tmp = [NSString stringWithFormat:@"%lu", token];

    [self setPrimitiveSectionIdentifier:tmp];
}

回复于 2024-04-29T12:12:34+08:00

NSFetchedResultsController组每4小时分成几个部分

1 回答

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