Getting array of unique objects

Question

I have an array of dates:

"2014-05-09 23:00:00 +0000",
"2014-05-09 23:00:00 +0000",
"2014-05-09 23:00:00 +0000",
"2014-05-09 23:00:00 +0000",
"2014-05-09 23:00:00 +0000",
"2014-05-09 23:00:00 +0000",
"2014-05-11 23:00:00 +0000",
"2014-05-11 23:00:00 +0000"

And i want to split this array to two different, and put in one array,

Result of what i want:

(
    "2014-05-09 23:00:00 +0000",
    "2014-05-09 23:00:00 +0000",
    "2014-05-09 23:00:00 +0000",
    "2014-05-09 23:00:00 +0000",
    "2014-05-09 23:00:00 +0000",
    "2014-05-09 23:00:00 +0000",

),
    (
    "2014-05-11 23:00:00 +0000",
    "2014-05-11 23:00:00 +0000"
)

Here's what i've tried:

self.tempDatesArray - array of dates (unique)
tempArray - array of all dates

self.tempDatesArray = [[[NSOrderedSet orderedSetWithArray:[self.tempDatesArray copy]] array] mutableCopy]; // i'm getting all the unique dates from array

if (self.tempDatesArray.count > 0){
                for (int j=0;j<self.tempDatesArray.count;j++){
                    if (tempArray[i] == self.tempDatesArray[j]){

                        [tempArray2 addObject:tempArray[i]]; // temp array

                        if (j++){

                            NSLog(@"i is %i",i);

                            [resultArray addObject:tempArray2];

                            NSLog(@"test %@",self.sectionsArray);

                            tempArray2 = [@[] mutableCopy];
                            }
                        }
                    }
            }

And my result is :

(
        "2014-05-09 23:00:00 +0000",
        "2014-05-09 23:00:00 +0000",
        "2014-05-09 23:00:00 +0000",
        "2014-05-09 23:00:00 +0000",
        "2014-05-09 23:00:00 +0000",
        "2014-05-09 23:00:00 +0000",
        "2014-05-11 23:00:00 +0000"
    ),
        (
        "2014-05-11 23:00:00 +0000"
    )

I'm little frustrated because of this, can some one put me in right direction?

You need to state the criteria you're using to separate dates. Do you want all the duplicates in 1 array and the rest in another array? As the other poster said, NSDate is really a wrapper around a double precision floating point number, so dates that appear the same may be off by a small fraction of a second and hence not compare as equal. — Duncan C
– Duncan C, Commented May 11, 2014 at 19:49
Or are you looking to separate your dates by day? In that case you might want to use NSCalendar and NSDateComponents to get the ordinal day value for each date and compare them. — Duncan C
– Duncan C, Commented May 11, 2014 at 19:52

iOSX · Accepted Answer · 2014-05-11 19:37:03Z

2

Yet another approach:

NSMutableArray *result = [NSMutableArray new];
[[arrayOfDates valueForKeyPath:@"@distinctUnionOfObjects.self"] enumerateObjectsUsingBlock:^(NSDate *date, NSUInteger idx, BOOL *stop) {

    NSIndexSet *indexSet = [arrayOfDates indexesOfObjectsPassingTest:^BOOL(NSDate *d, NSUInteger idx, BOOL *stop) {
        return [d isEqual:date];
    }];

    [result addObject:[arrayOfDates objectsAtIndexes:indexSet]];
}];

answered May 11, 2014 at 19:37

iOSX

1,30013 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Logan Over a year ago

What sorcery is this? Can you point me towards the docs mentioning this "distinctUnionOfObjects.self" and possibly other witchcraft?

iOSX Over a year ago

Sure :) developer.apple.com/library/ios/documentation/Cocoa/Conceptual/…

Logan Over a year ago

Well, I know what I'm doing today! I didn't know you could use keyValue stuff like this, thanks for the great info! This is why I come to StackOverflow . . . the things I had no idea I didn't know.

Logan · Accepted Answer · 2014-05-11 19:27:07Z

1

I think something like this should work:

NSArray * allDates = @[...];

NSSet * uniqueDates = [NSSet setWithArray:allDates];

NSMutableArray * groupedDatesArray = [NSMutableArray array];
for (NSDate * uniqueDate in uniqueDates) {
    NSMutableArray * sharedDateArray = [NSMutableArray array];
    for (NSDate * newDate in allDates) {
        if ([newDate isEqualToDate:uniqueDate]) {
            [sharedDateArray addObject:uniqueDate];
        }
    }
    [groupedDatesArray addObject:sharedDateArray];
}

NSLog(@"GroupedDates: %@", groupedDatesArray);

answered May 11, 2014 at 19:27

Logan

53.2k21 gold badges104 silver badges133 bronze badges

1 Comment

Vlad Z. Over a year ago

whoa, you're a life saver

bbarnhart · Accepted Answer · 2014-05-11 19:32:32Z

1

NSSet *set = [NSSet setWithArray:self.tempDateArray];
NSMutableArray  *groupedArray = [NSMutableArray array];

for (NSDate *date in [set allObjects]) {

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF = %@", date];
    NSArray *matchingArray = [self.tempDateArray filteredArrayUsingPredicate:predicate];
    [groupedArray addObject:matchingArray];
}

answered May 11, 2014 at 19:32

bbarnhart

6,7201 gold badge44 silver badges60 bronze badges

Comments

David Ogren · Accepted Answer · 2014-05-11 19:37:21Z

0

First, you say that you are looking for unique objects, but then in your expected results you have lots of duplicates. What are you really trying to do here?

I suspect that your second 2014-05-11 23:00:00 +0000 is getting lost because putting it into the ordered set is coalescing those into one entry. When the second 05-11 entry is added to the set, the set says "I already have that: it isn't unique".

Why aren't all of the duplicate 2014-05-09 23:00:00 entries getting coalesced then? I'm not sure. I'd have to see more of the code. Perhaps floating point issues. After all, NSDates are essentially big wrappers around floating points since a reference date. And comparing floating points is a fool's errand.

There are other things that confuse me about your code, but before I invest time trying to figure out what and why you are doing, do you really want to remove your duplicates? If so, what tolerance do you have between duplicates? Are 23:00:00 and 23:00:00.1 the same? 23:00:00.0001?

Or are you just trying to break down your arrays into subarrays based on day?

answered May 11, 2014 at 19:37

David Ogren

4,8752 gold badges22 silver badges31 bronze badges

1 Comment

Fattie Over a year ago

it's simply your last sentence there, David, the OP is after

Collectives™ on Stack Overflow

Getting array of unique objects

4 Answers 4

3 Comments

1 Comment

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

1 Comment

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related