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I have an array contains NSDictionary objects, and one key is Time, which contains time string format like "2013-10-09", and I need to sort the array by the Time key, but I don't know how to sort NSString with that format.

NOrder
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  • http://stackoverflow.com/questions/16208586/ios-sort-an-array-of-time-strings and http://stackoverflow.com/questions/1132806/sort-nsarray-of-date-strings-or-objects/1134126#1134126 – iPatel Oct 22 '13 at 06:44

3 Answers3

0
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];


NSMutableArray *dates = [NSMutableArray arrayWithCapacity:datesAry.count];
for (NSString *dateString in dates)
{
    NSDate *date = [dateFormatter dateFromString:timeString];
    [dates addObject:date];
}

[dates sortUsingSelector:@selector(compare:)];

NSMutableArray *sortedDates= [NSMutableArray arrayWithCapacity:dates.count];
for (NSDate *date in dates)
{
    NSString *dateString = [dateFormatter stringFromDate:date];
    [sortedDates addObject: dateString];
}
Rajneesh071
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    You should not use YYYY - "There are two things to note about this example: It uses yyyy to specify the year component. A common mistake is to use YYYY. yyyy specifies the calendar year whereas YYYY specifies the year (of “Week of Year”), used in the ISO year-week calendar. In most cases, yyyy and YYYY yield the same number, however they may be different. Typically you should use the calendar year." – adnako Oct 22 '13 at 07:03
0
- (void)testSortTimeAsString {
    NSDictionary *dict1 = @{@"key" : @"none", @"Time" : @"2013-10-01", @"optional" : @"---"};
    NSDictionary *dict2 = @{@"key" : @"none", @"Time" : @"2012-12-21", @"optional" : @"---"};
    NSDictionary *dict3 = @{@"key" : @"none", @"Time" : @"2013-02-10", @"optional" : @"---"};
    NSDictionary *dict4 = @{@"key" : @"none", @"Time" : @"2013-11-25", @"optional" : @"---"};
    NSDictionary *dict5 = @{@"key" : @"none", @"Time" : @"2013-06-15", @"optional" : @"---"};

    NSArray *array = @[dict1, dict2, dict3, dict4, dict5];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    dateFormatter.dateFormat = @"yyyy-MM-dd";

    NSArray *sorted = [array sortedArrayWithOptions:0 usingComparator:^(id obj1, id obj2) {
        NSString *stringDate1 = obj1[@"Time"];
        NSString *stringDate2 = obj2[@"Time"];

        NSDate *date1 = [dateFormatter dateFromString:stringDate1];
        NSDate *date2 = [dateFormatter dateFromString:stringDate2];

        NSComparisonResult result = [date1 compare:date2];
        return result;
    }];

    NSLog(@"Sorted array: \n%@", sorted);
}
adnako
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0

Sorting dates with that format have the same result as sorting them as strings. So:

  NSArray *unordered = @[
                         @{ @"Time": @"2001-01-01", @"Place" : @"Somewhere" },
                         @{ @"Time": @"1999-01-01", @"Place" : @"Elsewhere" },
                         @{ @"Time": @"1999-02-01", @"Place" : @"Nowhere" }
                         ];
  NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"Time" ascending:YES selector:@selector(compare:)];
  NSArray *ordered = [unordered sortedArrayUsingDescriptors:@[ sortDescriptor ]];

will give you the sorted array.

Tassos
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