Question

我的应用使用Core Data，我在CoreData Date中添加了一个属性。恢复值如下：

- (void)fetchedResults {
    // Core Data
    AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *context = [delegate managedObjectContext];

    // NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(date == %@) AND (date <= %@)", [_meetingArray valueForKey:@"when"], [_meetingArray valueForKey:@"when"]];
    // NSPredicate *predicate = [NSPredicate predicateWithFormat:@"listingID != %@", [_meetingArray valueForKey:@"when"]];

    NSFetchRequest *execQuery =[[NSFetchRequest alloc] init];
    NSEntityDescription *descOggetto = [NSEntityDescription entityForName:@"Meetings" inManagedObjectContext:context];
    [execQuery setEntity:descOggetto];
    // [execQuery setPredicate:predicate];

    NSError *error = nil;

    _meetingArray = [context executeFetchRequest:execQuery error:&error];
    _results = [context executeFetchRequest:execQuery error:&error];

    NSError *saveError = nil;
    [context save:&saveError];
}

使用方法 viewDidLoad ，我创建数组和词典，然后指示它们：

- (void)viewDidLoad {
    [super viewDidLoad];
    [self fetchedResults];

    _myArr = [NSArray arrayWithObject:[_meetingArray valueForKey:@"when"]];
    _myDict = [NSMutableDictionary dictionaryWithObject:_myArr forKey:@"when"];

    _unsortedDays = _myDict[@"when"][0];
    _sortedDays = [_unsortedDays sortedArrayUsingSelector:@selector(compare:)];

    NSLog(@"unsorted: %@, sorted: %@", _unsortedDays, _sortedDays);
    NSLog(@"sorted count: %ld", _sortedDays.count);

}

并且来自此输出：

2014-03-19 18:38:32.218 GroupData[8815:70b] unsorted: (
    "2014-03-19 16:00:33 +0000",
    "2014-03-20 17:00:33 +0000",
    "2014-03-21 14:00:33 +0000",
    "2014-03-17 14:00:33 +0000",
    "2014-03-18 15:00:33 +0000",
    "2014-03-20 17:45:56 +0000",
    "2014-03-20 17:45:56 +0000"
), sorted: (
    "2014-03-17 14:00:33 +0000",
    "2014-03-18 15:00:33 +0000",
    "2014-03-19 16:00:33 +0000",
    "2014-03-20 17:00:33 +0000",
    "2014-03-20 17:45:56 +0000",
    "2014-03-20 17:45:56 +0000",
    "2014-03-21 14:00:33 +0000"
)
2014-03-19 18:38:32.219 GroupData[8815:70b] sorted count: 7

现在，如何删除重复的结果？

Answer 1

NSSet怎么样？

NSSet aSet = [NSSet setWithArray: _unsortedDays];

现在 unsortedDays 数组中的所有字符串都是 aSet 对象。

您希望数据作为数组退出集合中吗？

_unsortedNoDupes = [aSet allObjects] ;

我希望这就是你要找的东西？

Answer 2

您需要遍历日期，将日期部分存储在集合中，并删除日期（如果已使用）。

此代码会将日期的一部分转换为字符串，如果之前遇到过日期字符串，则从数组中删除该项目。

NSMutableSet *usedDays = [NSMutableSet new];
for (int i=0; i<[_sortedDays count]; i++) {
    NSDate *date = _sortedDays[i];
    NSString *dateString = [date descriptionWithCalendarFormat:@"%Y-%m-%d" timeZone:nil locale:nil];

    if ([usedDays containsObject:dateString]) {
        // This day has already been used. Remove this date from the array.
        [_sortedDays removeObjectAtIndex:i];
        i--;
    } else {
        // This is a new day, mark it as having been used
        [usedDays addObject:dateString];
    }
}

请注意，如果日期来自不同的区域设置/时区，您可能会遇到问题。在这种情况下，请确保它们已规范化，并且说明使用您在代码中其他位置使用的相同区域设置。

如何只用一天来过滤这个数组的日期？

2 个答案: