CoreData 按即将到来的生日排序

Question

我正在 xcode 中构建我的第一个应用程序，并尝试使用 coreData 和 NSFetchedResultController 获取按即将到来的生日排序的人员列表。我的实体设置如下

uBirthdays
--------------
NSString uName
NSDate uBday

这是我当前的代码：

- (NSFetchedResultsController *)fetchedResultsController {

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

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"uBirthdays" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];

NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"uBday" ascending:YES];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"sectionNameGen" cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;

[sort release];
[fetchRequest release];
[theFetchedResultsController release];

return _fetchedResultsController;    

}

是否可以按即将到来的生日对其进行排序？或者我是否必须将我的生日非标准化，以便我只能按月和日排序？任何意见都将受到高度赞赏。

谢谢

Answer 1

这是你可以做的。

1) 为您的 uBDay 和 uName 设置 NSSortDescriptors ，以便您的记录将首先按生日排序，然后按姓名排序。

2) 创建一个 NSPredicate 来提取 [NSDate now] （即今天）到未来某个时间（即未来 30 天 = [NSDate dateWithTimeIntervalSinceNow:kOneDayTimeInterval*30])

示例代码如下：

#define kOneDayTimeInterval 86400 // this is in seconds: 86400 = 1 day

    - (NSFetchedResultsController *)fetchedResultsController {
        ...
        NSSortDescriptor *sortByBDay = [[NSSortDescriptor alloc] initWithKey:@"uBday" ascending:YES];
        NSSortDescriptor *sortByName = [[NSSortDescriptor alloc] initWithKey:@"uName" ascending:YES];
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortByBDay,sortByName, nil];
        [fetchRequest setSortDescriptors:sortDescriptors];
        [sortDescriptors release];
        [sortByName release];
        [sortByReleaseDate release];            
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(uBDay > %@) AND (uBDay <= %@)", [NSDate date], [NSDate dateWithTimeIntervalSinceNow:kOneDayTimeInterval*30]];
        [fetchRequest setPredicate:predicate];
        ...