CODEWITHSUNDEEP
objective-ccocoasortingnsarraynsdate
postalservice14
postalservice14

Reputation: 2534

Sort NSArray of date strings or objects

I have an NSArray that contains date strings (i.e. NSString) like this: "Thu, 21 May 09 19:10:09 -0700"

I need to sort the NSArray by date. I thought about converting the date string to an NSDate object first, but got stuck there on how to sort by the NSDate object.

Thanks.

Upvotes: 87

Views: 83635

Answers (9)

Quinn Taylor
Quinn Taylor

Reputation: 44769

Store the dates as NSDate objects in an NS(Mutable)Array, then use -[NSArray sortedArrayUsingSelector: or -[NSMutableArray sortUsingSelector:] and pass @selector(compare:) as the parameter. The -[NSDate compare:] method will order dates in ascending order for you. This is simpler than creating an NSSortDescriptor, and much simpler than writing your own comparison function. (NSDate objects know how to compare themselves to each other at least as efficiently as we could hope to accomplish with custom code.)

Upvotes: 112

notnoop
notnoop

Reputation: 59299

You can use sortedArrayUsingFunction:context:. Here is a sample:

NSComparisonResult dateSort(NSString *s1, NSString *s2, void *context) {
    NSDate *d1 = [NSDate dateWithString:s1];
    NSDate *d2 = [NSDate dateWithString:s2];
    return [d1 compare:d2];
}

NSArray *sorted = [unsorted sortedArrayUsingFunction:dateSort context:nil];

When using a NSMutableArray, you can use sortArrayUsingFunction:context: instead.

Upvotes: 5

Abhishek Jain
Abhishek Jain

Reputation: 4739

Swift 3.0

myMutableArray = myMutableArray.sorted(by: { $0.date.compare($1.date) == ComparisonResult.orderedAscending })

Upvotes: 2

TheCodingArt
TheCodingArt

Reputation: 3429

You may also use something like the following: 

//Sort the array of items by  date
    [self.items sortUsingComparator:^NSComparisonResult(id obj1, id obj2){
        return [obj2.date compare:obj1.date];
    }];

But this does assume that the date is stored as a NSDate rather a NString, which should be no problem to make/do. Preferably, I recommend also storing the data in it's raw format. Makes it easier to manipulate in situations like this.

Upvotes: 17

Javier Calatrava Llavería
Javier Calatrava Llavería

Reputation: 9649

What it worked in my case was the following:

    NSArray *aUnsorted = [dataToDb allKeys];
    NSArray *arrKeys = [aUnsorted sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        NSDateFormatter *df = [[NSDateFormatter alloc] init];
        [df setDateFormat:@"dd-MM-yyyy"];
        NSDate *d1 = [df dateFromString:(NSString*) obj1];
        NSDate *d2 = [df dateFromString:(NSString*) obj2];
        return [d1 compare: d2];
    }];

I had a dictionary, where all keys where dates in format dd-MM-yyyy. And allKeys returns the dictionary keys unsorted, and I wanted to present the data in chronological order.

Upvotes: 5

user2339385
user2339385

Reputation: 17

Change this 

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"beginDate" ascending:TRUE];
[myMutableArray sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];

To

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Date" ascending:TRUE];
[myMutableArray sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];

Just change the KEY: it must be Date always

Upvotes: 1

smorgan
smorgan

Reputation: 21569

Once you have an NSDate, you can create an NSSortDescriptor with initWithKey:ascending: and then use sortedArrayUsingDescriptors: to do the sorting.

Upvotes: 4

vinzenzweber
vinzenzweber

Reputation: 3389

If I have an NSMutableArray of objects with a field "beginDate" of type NSDate I am using an NSSortDescriptor as below:

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"beginDate" ascending:TRUE];
[myMutableArray sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];

Upvotes: 115

Kostiantyn Sokolinskyi
Kostiantyn Sokolinskyi

Reputation: 781

You can use blocks to sort in place:

sortedDatesArray = [[unsortedDatesArray sortedArrayUsingComparator: ^(id a, id b) {
    NSDate *d1 = [NSDate dateWithString: s1];
    NSDate *d2 = [NSDate dateWithString: s2];
    return [d1 compare: d2];
}];

I suggest you convert all your strings to dates before sorting not to do the conversion more times than there are date items. Any sorting algorithm will give you more string to date conversions than the number of items in the array (sometimes substantially more)

a bit more on blocks sorting: http://sokol8.blogspot.com/2011/04/sorting-nsarray-with-blocks.html

Upvotes: 10

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