By rustyshelf


2009-04-30 06:10:56 8 Comments

What I want to do seems pretty simple, but I can't find any answers on the web. I have an NSMutableArray of objects, and let's say they are 'Person' objects. I want to sort the NSMutableArray by Person.birthDate which is an NSDate.

I think it has something to do with this method:

NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(???)];

In Java I would make my object implement Comparable, or use Collections.sort with an inline custom comparator...how on earth do you do this in Objective-C?

25 comments

@Arvind Patel 2018-06-14 09:21:27

You use NSSortDescriptor to sort an NSMutableArray with custom objects

 NSSortDescriptor *sortingDescriptor;
 sortingDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                       ascending:YES];
 NSArray *sortArray = [drinkDetails sortedArrayUsingDescriptors:@[sortDescriptor]];

@Parth Barot 2018-04-12 10:32:49

You have to create sortDescriptor and then you can sort the nsmutablearray by using sortDescriptor like below.

 let sortDescriptor = NSSortDescriptor(key: "birthDate", ascending: true, selector: #selector(NSString.compare(_:)))
 let array = NSMutableArray(array: self.aryExist.sortedArray(using: [sortDescriptor]))
 print(array)

@Syed Qamar Abbas 2018-03-24 21:20:34

Sort Array In Swift


For Swifty Person below is a very clean technique to achieve above goal for globally. Lets have an example custom class of User which have some attributes.

class User: NSObject {
    var id: String?
    var name: String?
    var email: String?
    var createdDate: Date?
}

Now we have an array which we need to sort on the basis of createdDate either ascending and/or descending. So lets add a function for date comparison.

class User: NSObject {
    var id: String?
    var name: String?
    var email: String?
    var createdDate: Date?
    func checkForOrder(_ otherUser: User, _ order: ComparisonResult) -> Bool {
        if let myCreatedDate = self.createdDate, let othersCreatedDate = otherUser.createdDate {
            //This line will compare both date with the order that has been passed.
            return myCreatedDate.compare(othersCreatedDate) == order
        }
        return false
    }
}

Now lets have an extension of Array for User. In simple words lets add some methods only for those Array's which only have User objects in it.

extension Array where Element: User {
    //This method only takes an order type. i.e ComparisonResult.orderedAscending
    func sortUserByDate(_ order: ComparisonResult) -> [User] {
        let sortedArray = self.sorted { (user1, user2) -> Bool in
            return user1.checkForOrder(user2, order)
        }
        return sortedArray
    }
}

Usage for Ascending Order

let sortedArray = someArray.sortUserByDate(.orderedAscending)

Usage for Descending Order

let sortedArray = someArray.sortUserByDate(.orderedAscending)

Usage for Same Order

let sortedArray = someArray.sortUserByDate(.orderedSame)

Above method in extension will only be accessible if the Array is of type [User] || Array<User>

@Emre Gürses 2016-12-13 12:22:14

In my case, I use "sortedArrayUsingComparator" to sort an array. Look at the below code.

contactArray = [[NSArray arrayWithArray:[contactSet allObjects]] sortedArrayUsingComparator:^NSComparisonResult(ContactListData *obj1, ContactListData *obj2) {
    NSString *obj1Str = [NSString stringWithFormat:@"%@ %@",obj1.contactName,obj1.contactSurname];
    NSString *obj2Str = [NSString stringWithFormat:@"%@ %@",obj2.contactName,obj2.contactSurname];
    return [obj1Str compare:obj2Str];
}];

Also my object is,

@interface ContactListData : JsonData
@property(nonatomic,strong) NSString * contactName;
@property(nonatomic,strong) NSString * contactSurname;
@property(nonatomic,strong) NSString * contactPhoneNumber;
@property(nonatomic) BOOL isSelected;
@end

@Georg Schölly 2009-04-30 06:25:03

Compare method

Either you implement a compare-method for your object:

- (NSComparisonResult)compare:(Person *)otherObject {
    return [self.birthDate compare:otherObject.birthDate];
}

NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(compare:)];

NSSortDescriptor (better)

or usually even better:

NSSortDescriptor *sortDescriptor;
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                           ascending:YES];
NSArray *sortedArray = [drinkDetails sortedArrayUsingDescriptors:@[sortDescriptor]];

You can easily sort by multiple keys by adding more than one to the array. Using custom comparator-methods is possible as well. Have a look at the documentation.

Blocks (shiny!)

There's also the possibility of sorting with a block since Mac OS X 10.6 and iOS 4:

NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
    NSDate *first = [(Person*)a birthDate];
    NSDate *second = [(Person*)b birthDate];
    return [first compare:second];
}];

Performance

The -compare: and block-based methods will be quite a bit faster, in general, than using NSSortDescriptor as the latter relies on KVC. The primary advantage of the NSSortDescriptor method is that it provides a way to define your sort order using data, rather than code, which makes it easy to e.g. set things up so users can sort an NSTableView by clicking on the header row.

@Martin Gjaldbaek 2011-05-17 08:52:53

The first example has a bug: You compare the birthDate instance variable in one object with the other object itself, rather than its birthDate variable.

@Georg Schölly 2011-05-17 11:18:17

@Martin: Thanks! Funny that nobody else noticed before I got 75 upvotes for it.

@jpswain 2011-12-02 20:30:26

Because this is the accepted answer, and therefore probably considered definitive by most users, it might be helpful to add a 3rd, block-based example so that users will be aware it exists too.

@Georg Schölly 2011-12-04 20:25:21

@orange80: I tried that. I don't own a Mac any more, so it would be nice if you could look at the code.

@fishinear 2011-12-09 20:42:01

You can also declare the parameters of the block with the correct type already, reducing the sorting to: [drinkDetails sortedArrayUsingComparator:^(Person* a, Person* b) { return [a.birthDate compare:b.birthDate]; }]

@Georg Schölly 2011-12-10 15:42:02

@fishinear: Are you sure? I've haven't used blocks yet myself, but looking at other examples it seems that everyone uses id as the arguments. Example: Question 1, Question 2.

@TPoschel 2012-04-12 19:05:22

In the case where birthDate is null and you want those to show up at the end of the sorted array you can do this: NSDate *first = [(Person *)a birthDate] ? [a birthDate]:[NSDate distantFuture];

@Lithu T.V 2012-06-06 06:41:54

so how about case insensitive sort on an nsstring object comparison using second method??

@Georg Schölly 2012-06-06 15:25:12

@Lithu: Did you look at the documentation. It's basically directly in there. If you don't find out how to do it, ask in a new question.

@Lithu T.V 2012-06-07 12:10:46

@GeorgSchölly : yup worked it out by docs..frgt to update the cmnt :)

@Lithu T.V 2012-06-07 12:13:14

k here is the answer for wht i hav asked ,ie about case sensitive nd case insensitive sort.there is one more method in sort descriptor which defines the selector :- sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"title" ascending:YES selector:@selector(caseInsensitiveCompare:)] autorelease];

@kubilay 2012-07-23 12:38:46

Thank you! That's a solution for issue about ordering accented characters in SQLite.

@Stephan 2012-08-06 06:01:43

If you have a NSMutableArray i prefer to use the methodes sortUsingDescriptors , sortUsingFunction or sortUsingSelector. As far as the array is mutable I usually don't need a sorted copy.

@Hiren 2012-10-21 13:43:51

I have used block option for sort. it's work great. but i have another problem i have to sort an array using condition. like i have two values "Company" and "Date". if the company name is same then it check date which would be latest it first sort can you help me out ?

@marciokoko 2013-02-14 04:04:41

What if I have an array with latitude and longitude and I want to sort by distance from userLocation. I've calculated the distance to each. Do I create a new array with the distance value?

@Georg Schölly 2013-02-14 19:59:54

@marciokoko: Open a new questions, comments are not a good place for this. :)

@marciokoko 2013-02-14 20:08:00

Thanks Georg, here it is: stackoverflow.com/questions/14879486/…

@Accatyyc 2013-03-12 09:47:25

Just wanted to add - the answer to the question asked by @HiRen isn't for another question. This is exactly what the sort descriptors in this example are for. Maybe this post should explain that you can use multiple sort descriptors to sort by many keys?

@Georg Schölly 2013-03-12 14:57:17

@Accatyyc: I added a small paragraph about it. I didn't want to increase the complexity of the answer too much.

@stefanB 2013-05-24 00:30:36

@Matthew Knippen 2014-02-17 16:25:30

this should be updated to include literals, so future people looking at this code can see updated syntax, and how it's now being done.

@bcattle 2014-03-06 09:58:06

Not to beat a dead horse but its potentially be worth noting that sortedUsingComparator sorts in-place with a NSMutableArray, potentially a more common use case.

@AlKozin 2014-03-11 12:36:49

And what is the best/fastest sorting method?

@KarenAnne 2014-04-04 10:10:48

The third one is the best option? @GeorgSchölly

@Georg Schölly 2014-04-06 20:13:02

@Karen: It depends. Use the compare method if there is a natural ordering between your objects. If it's a simple comparison, use a block. And finally if your comparison is tricky and uses lots of logic, an NSSortDescriptor probably makes the most sense.

@Septronic 2015-12-30 12:14:12

I love the block as well, I've used it in a couple of projects I was working on, and they never failed me! Block to the rescue! :) ( and Georg )

@Sid 2016-01-19 13:20:57

Perfectly Explained.

@Cindeselia 2016-05-02 03:23:49

Where does the compare method go? In the implementation of the custom object being sorted in the NSMutableArray, or in the implementation of the class doing the sorting? I sense it should be in the custom object's implementation (from the self.birthdate), but the formatting of the answer makes it seem like it's the same .m file as the call to sort the array, so I wanted to check to make sure. From the standpoint of a programming beginner, it's not obvious at all where to put snippets of code even if it might seem second nature to a vet.

@Georg Schölly 2016-05-02 12:43:00

You're right, it goes into the implementation of the custom object.

@James Rochabrun 2017-03-27 22:14:35

Swift's protocols and functional programming makes that very easy you just have to make your class conform to the Comparable protocol, implement the methods required by the protocol and then use the sorted(by: ) high order function to create a sorted array without need to use mutable arrays by the way.

class Person: Comparable {
    var birthDate: NSDate?
    let name: String

    init(name: String) {
        self.name = name
    }

    static func ==(lhs: Person, rhs: Person) -> Bool {
        return lhs.birthDate === rhs.birthDate || lhs.birthDate?.compare(rhs.birthDate as! Date) == .orderedSame
    }

    static func <(lhs: Person, rhs: Person) -> Bool {
        return lhs.birthDate?.compare(rhs.birthDate as! Date) == .orderedAscending
    }

    static func >(lhs: Person, rhs: Person) -> Bool {
        return lhs.birthDate?.compare(rhs.birthDate as! Date) == .orderedDescending
    }

}

let p1 = Person(name: "Sasha")
p1.birthDate = NSDate() 

let p2 = Person(name: "James")
p2.birthDate = NSDate()//he is older by miliseconds

if p1 == p2 {
    print("they are the same") //they are not
}

let persons = [p1, p2]

//sort the array based on who is older
let sortedPersons = persons.sorted(by: {$0 > $1})

//print sasha which is p1
print(persons.first?.name)
//print James which is the "older"
print(sortedPersons.first?.name)

@Fernando Redondo 2010-11-22 10:51:34

I tried all, but this worked for me. In a class I have another class named "crimeScene", and want to sort by a property of "crimeScene".

This works like a charm:

NSSortDescriptor *sorter = [[NSSortDescriptor alloc] initWithKey:@"crimeScene.distance" ascending:YES];
[self.arrAnnotations sortUsingDescriptors:[NSArray arrayWithObject:sorter]];

@Kostiantyn Sokolinskyi 2011-04-14 09:03:10

iOS 4 blocks will save you :)

featuresArray = [[unsortedFeaturesArray sortedArrayUsingComparator: ^(id a, id b)  
{
    DMSeatFeature *first = ( DMSeatFeature* ) a;
    DMSeatFeature *second = ( DMSeatFeature* ) b;

    if ( first.quality == second.quality )
        return NSOrderedSame;
    else
    {
        if ( eSeatQualityGreen  == m_seatQuality || eSeatQualityYellowGreen == m_seatQuality || eSeatQualityDefault  == m_seatQuality )
        {
            if ( first.quality < second.quality )
                return NSOrderedAscending;
            else
                return NSOrderedDescending;
        }
        else // eSeatQualityRed || eSeatQualityYellow
        {
            if ( first.quality > second.quality )
                return NSOrderedAscending;
            else
                return NSOrderedDescending;
        } 
    }
}] retain];

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

@Aamir 2016-06-16 09:32:26

Sort using NSComparator

If we want to sort custom objects we need to provide NSComparator, which is used to compare custom objects. The block returns an NSComparisonResult value to denote the ordering of the two objects. So in order to sort whole array NSComparator is used in following way.

NSArray *sortedArray = [employeesArray sortedArrayUsingComparator:^NSComparisonResult(Employee *e1, Employee *e2){
    return [e1.firstname compare:e2.firstname];    
}];

Sorts Using NSSortDescriptor
Let’s assume, as an example, that we have an array containing instances of a custom class, Employee has attributes firstname, lastname and age. The following example illustrates how to create an NSSortDescriptor that can be used to sort the array contents in ascending order by the age key.

NSSortDescriptor *ageDescriptor = [[NSSortDescriptor alloc] initWithKey:@"age" ascending:YES];
NSArray *sortDescriptors = @[ageDescriptor];
NSArray *sortedArray = [employeesArray sortedArrayUsingDescriptors:sortDescriptors];

Sort using Custom Comparisons
Names are strings, and when you sort strings to present to the user you should always use a localized comparison. Often you also want to perform a case insensitive comparison. Here comes an example with (localizedStandardCompare:) to order the array by last and first name.

NSSortDescriptor *lastNameDescriptor = [[NSSortDescriptor alloc]
              initWithKey:@"lastName" ascending:YES selector:@selector(localizedStandardCompare:)];
NSSortDescriptor * firstNameDescriptor = [[NSSortDescriptor alloc]
              initWithKey:@"firstName" ascending:YES selector:@selector(localizedStandardCompare:)];
NSArray *sortDescriptors = @[lastNameDescriptor, firstNameDescriptor];
NSArray *sortedArray = [employeesArray sortedArrayUsingDescriptors:sortDescriptors];

For reference and detailed discussion please refer: https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/SortDescriptors/Articles/Creating.html
http://www.ios-blog.co.uk/tutorials/objective-c/how-to-sort-nsarray-with-custom-objects/

@Alex Reynolds 2009-04-30 06:24:09

See the NSMutableArray method sortUsingFunction:context:

You will need to set up a compare function which takes two objects (of type Person, since you are comparing two Person objects) and a context parameter.

The two objects are just instances of Person. The third object is a string, e.g. @"birthDate".

This function returns an NSComparisonResult: It returns NSOrderedAscending if PersonA.birthDate < PersonB.birthDate. It will return NSOrderedDescending if PersonA.birthDate > PersonB.birthDate. Finally, it will return NSOrderedSame if PersonA.birthDate == PersonB.birthDate.

This is rough pseudocode; you will need to flesh out what it means for one date to be "less", "more" or "equal" to another date (such as comparing seconds-since-epoch etc.):

NSComparisonResult compare(Person *firstPerson, Person *secondPerson, void *context) {
  if ([firstPerson birthDate] < [secondPerson birthDate])
    return NSOrderedAscending;
  else if ([firstPerson birthDate] > [secondPerson birthDate])
    return NSOrderedDescending;
  else 
    return NSOrderedSame;
}

If you want something more compact, you can use ternary operators:

NSComparisonResult compare(Person *firstPerson, Person *secondPerson, void *context) {
  return ([firstPerson birthDate] < [secondPerson birthDate]) ? NSOrderedAscending : ([firstPerson birthDate] > [secondPerson birthDate]) ? NSOrderedDescending : NSOrderedSame;
}

Inlining could perhaps speed this up a little, if you do this a lot.

@Georg Schölly 2009-04-30 06:28:40

Using sortUsingFunction:context: is probably the most c-ish way and definitly the most unreadable one.

@Alex Reynolds 2009-04-30 06:32:13

What's wrong with a "c-ish" approach? It works fine.

@Georg Schölly 2009-04-30 06:43:54

There's nothing really wrong with it, but I think there are now much better alternatives.

@Alex Reynolds 2009-04-30 06:51:51

Perhaps, but I don't think it would be any less readable to someone from a Java background who might be looking for something similar to Java's abstract Comparator class, which implements compare(Type obj1, Type obj2).

@freespace 2009-05-01 16:28:05

I think the biggest stumbling block to using sortUsingFunction for some one with out a solid C background would be: a) realising it wants a function pointer; b) get used to the idea of a function pointer; c) parse the function pointer so as to construct the required function.

@Alex Reynolds 2009-05-01 17:59:13

I get the sense a couple of you are looking for any reason whatsoever to criticize this perfectly fine answer, even if that criticism has very little technical merit. Weird.

@Dan Rosenstark 2010-12-16 22:34:35

@Georg, the problem with your answer above, and the advantages to Alex's method here, is that you get one compare method per class. So if you need to compare on multiple criteria, you must use sortUsingFunction:content:, Right?

@Georg Schölly 2010-12-17 11:38:19

@Yar: Either you can use the solution I provided in the first paragraph, or you use multiple sort descriptors. sortedArrayUsingDescriptors: takes an array of sort descriptors as argument.

@yannis 2012-09-21 09:18:35

@Jeroen Hi! When you are going to reject an edit, just reject it, don't click "improve" if you don't actually mean to improve the edit. Rejecting the edits here was a good call, but by going through improve you've created two nonsensical revisions to the question.

@Asciiom 2012-09-21 09:19:33

I know, you are right, I had a moment of confusion here because of doing 3 things at once. Won't happen again ;)

@leviathan 2011-03-16 18:46:26

Starting in iOS 4 you can also use blocks for sorting.

For this particular example I'm assuming that the objects in your array have a 'position' method, which returns an NSInteger.

NSArray *arrayToSort = where ever you get the array from... ;
NSComparisonResult (^sortBlock)(id, id) = ^(id obj1, id obj2) 
{
    if ([obj1 position] > [obj2 position]) 
    { 
        return (NSComparisonResult)NSOrderedDescending;
    }
    if ([obj1 position] < [obj2 position]) 
    {
        return (NSComparisonResult)NSOrderedAscending;
    }
    return (NSComparisonResult)NSOrderedSame;
};
NSArray *sorted = [arrayToSort sortedArrayUsingComparator:sortBlock];

Note: the "sorted" array will be autoreleased.

@Mohit 2011-09-06 09:44:57

Sorting NSMutableArray is very simple:

NSMutableArray *arrayToFilter =
     [[NSMutableArray arrayWithObjects:@"Photoshop",
                                       @"Flex",
                                       @"AIR",
                                       @"Flash",
                                       @"Acrobat", nil] autorelease];

NSMutableArray *productsToRemove = [[NSMutableArray array] autorelease];

for (NSString *products in arrayToFilter) {
    if (fliterText &&
        [products rangeOfString:fliterText
                        options:NSLiteralSearch|NSCaseInsensitiveSearch].length == 0)

        [productsToRemove addObject:products];
}
[arrayToFilter removeObjectsInArray:productsToRemove];

@roocell 2011-05-08 23:27:45

I've used sortUsingFunction:: in some of my projects:

int SortPlays(id a, id b, void* context)
{
    Play* p1 = a;
    Play* p2 = b;
    if (p1.score<p2.score) 
        return NSOrderedDescending;
    else if (p1.score>p2.score) 
        return NSOrderedAscending;
    return NSOrderedSame;
}

...
[validPlays sortUsingFunction:SortPlays context:nil];

@Hardik Darji 2011-03-30 05:54:36

NSSortDescriptor *sortDescriptor;
sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"birthDate" ascending:YES] autorelease];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingDescriptors:sortDescriptors];

Thanks, it's working fine...

@Manuel Spuhler 2009-05-06 16:25:51

There is a missing step in Georg Schölly's second answer, but it works fine then.

NSSortDescriptor *sortDescriptor;
sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                              ascending:YES] autorelease];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingDescriptor:sortDescriptors];

@LucasTizma 2009-05-13 19:58:37

The method call is actually "sortedArrayUsingDescriptors:", with an 's' at the end.

@Georg Schölly 2009-06-15 16:20:17

Thanks, haven't seen that 's'.

@MD Aslam Ansari 2015-04-16 09:17:48

You can use the following generic method for your purpose. It should solve your issue.

//Called method
-(NSMutableArray*)sortArrayList:(NSMutableArray*)arrDeviceList filterKeyName:(NSString*)sortKeyName ascending:(BOOL)isAscending{
    NSSortDescriptor *sorter = [[NSSortDescriptor alloc] initWithKey:sortKeyName ascending:isAscending];
    [arrDeviceList sortUsingDescriptors:[NSArray arrayWithObject:sorter]];
    return arrDeviceList;
}

//Calling method
[self sortArrayList:arrSomeList filterKeyName:@"anything like date,name etc" ascending:YES];

@user3622576 2015-01-05 07:00:45

NSSortDescriptor  *sort = [[NSSortDescriptor alloc] initWithKey:@"_strPrice"
                                                 ascending:sortFlag selector:@selector(localizedStandardCompare:)] ;

@Boobalan 2013-06-04 10:09:00

I just done multi level sorting based on custom requirement.

//sort the values

    [arrItem sortUsingComparator:^NSComparisonResult (id a, id b){

    ItemDetail * itemA = (ItemDetail*)a;
    ItemDetail* itemB =(ItemDetail*)b;

    //item price are same
    if (itemA.m_price.m_selling== itemB.m_price.m_selling) {

        NSComparisonResult result=  [itemA.m_itemName compare:itemB.m_itemName];

        //if item names are same, then monogramminginfo has to come before the non monograme item
        if (result==NSOrderedSame) {

            if (itemA.m_monogrammingInfo) {
                return NSOrderedAscending;
            }else{
                return NSOrderedDescending;
            }
        }
        return result;
    }

    //asscending order
    return itemA.m_price.m_selling > itemB.m_price.m_selling;
}];

https://sites.google.com/site/greateindiaclub/mobil-apps/ios/multilevelsortinginiosobjectivec

@Siddhesh Bondre 2013-10-29 01:28:27

NSMutableArray *stockHoldingCompanies = [NSMutableArray arrayWithObjects:fortune1stock,fortune2stock,fortune3stock,fortune4stock,fortune5stock,fortune6stock , nil];

NSSortDescriptor *sortOrder = [NSSortDescriptor sortDescriptorWithKey:@"companyName" ascending:NO];

[stockHoldingCompanies sortUsingDescriptors:[NSArray arrayWithObject:sortOrder]];

NSEnumerator *enumerator = [stockHoldingCompanies objectEnumerator];

ForeignStockHolding *stockHoldingCompany;

NSLog(@"Fortune 6 companies sorted by Company Name");

    while (stockHoldingCompany = [enumerator nextObject]) {
        NSLog(@"===============================");
        NSLog(@"CompanyName:%@",stockHoldingCompany.companyName);
        NSLog(@"Purchase Share Price:%.2f",stockHoldingCompany.purchaseSharePrice);
        NSLog(@"Current Share Price: %.2f",stockHoldingCompany.currentSharePrice);
        NSLog(@"Number of Shares: %i",stockHoldingCompany.numberOfShares);
        NSLog(@"Cost in Dollars: %.2f",[stockHoldingCompany costInDollars]);
        NSLog(@"Value in Dollars : %.2f",[stockHoldingCompany valueInDollars]);
    }
    NSLog(@"===============================");

@DenTheMan 2010-11-09 13:47:20

For NSMutableArray, use the sortUsingSelector method. It sorts it-place, without creating a new instance.

@jmathew 2013-11-17 19:01:18

Just an update: I too was looking for something that sorted the mutable array in place, there are now "sortUsing" equivalent methods for all the "sortedArrayUsing" methods as of iOS 7. Such as sortUsingComparator:.

@Dinesh_ 2012-12-06 07:51:07

If you're just sorting an array of NSNumbers, you can sort them with 1 call:

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

That works because the objects in the array (NSNumber objects) implement the compare method. You could do the same thing for NSString objects, or even for an array of custom data objects that implement a compare method.

Here's some example code using comparator blocks. It sorts an array of dictionaries where each dictionary includes a number in a key "sort_key".

#define SORT_KEY @\"sort_key\"

[anArray sortUsingComparator: 
 ^(id obj1, id obj2) 
  {
  NSInteger value1 = [[obj1 objectForKey: SORT_KEY] intValue];
  NSInteger value2 = [[obj2 objectForKey: SORT_KEY] intValue];
  if (value1 > value2) 
{
  return (NSComparisonResult)NSOrderedDescending;
  }

  if (value1 < value2) 
{
  return (NSComparisonResult)NSOrderedAscending;
  }
    return (NSComparisonResult)NSOrderedSame;
 }];

The code above goes through the work of getting an integer value for each sort key and comparing them, as an illustration of how to do it. Since NSNumber objects implement a compare method, it could be rewritten much more simply:

 #define SORT_KEY @\"sort_key\"

[anArray sortUsingComparator: 
^(id obj1, id obj2) 
 {
  NSNumber* key1 = [obj1 objectForKey: SORT_KEY];
  NSNumber* key2 = [obj2 objectForKey: SORT_KEY];
  return [key1 compare: key2];
 }];

or the body of the comparator could even be distilled down to 1 line:

  return [[obj1 objectForKey: SORT_KEY] compare: [obj2 objectForKey: SORT_KEY]];

I tend to prefer simple statements and lots of temporary variables because the code is easier to read, and easier to debug. The compiler optimizes away the temporary variables anyway, so there is no advantage to the all-in-one-line version.

@Chris 2011-03-24 22:15:46

I did this in iOS 4 using a block. Had to cast the elements of my array from id to my class type. In this case it was a class called Score with a property called points.

Also you need to decide what to do if the elements of your array are not the right type, for this example I just returned NSOrderedSame, however in my code I though an exception.

NSArray *sorted = [_scores sortedArrayUsingComparator:^(id obj1, id obj2){
    if ([obj1 isKindOfClass:[Score class]] && [obj2 isKindOfClass:[Score class]]) {
        Score *s1 = obj1;
        Score *s2 = obj2;

        if (s1.points > s2.points) {
            return (NSComparisonResult)NSOrderedAscending;
        } else if (s1.points < s2.points) {
            return (NSComparisonResult)NSOrderedDescending;
        }
    }

    // TODO: default is the same?
    return (NSComparisonResult)NSOrderedSame;
}];

return sorted;

PS: This is sorting in descending order.

@jpswain 2011-12-02 20:28:46

You don't actually need the "(Score *)" casts in there, you can just do "Score *s1 = obj1;" because id will happily cast to anything without warning from the compiler :-)

@thesummersign 2012-05-03 10:48:58

right orange80 downcasting doesn't requires a cast before the weak variable.

@Chris 2012-05-06 10:20:10

Thanks guys, I've removed the cast from the answer

@Scott Corscadden 2012-08-08 18:53:47

You should sort nil vs. not-nil to the top or bottom consistently, so the default end return might be return ((!obj1 && !obj2) ? NSOrderedSame : (obj1 ? NSOrderedAscending : NSOrderedDescending))

@Nikesh K 2012-09-13 07:12:50

heh Chris, i tried this code, I do hv a refresh in my program.. for the first time i does correct job, got a descending order output.. but when i refresh.( execute the same code with same data ) it changed the order, it was not descending.. Say i hv 4 objects in my array, 3 hv same data, 1 is differed.

@gnasher729 2014-02-17 14:57:11

If you actually expect objects that are not of the "Score" class, you need to sort them a bit more careful. Otherwise you have a situation where other == score1 < score2 == other which is inconsistent and could lead to trouble. You could return a value that implies Score objects sort before all other objects, and all other objects sort equal to each other.

@ColinE 2013-03-06 08:29:13

I have created a small library of category methods, called Linq to ObjectiveC, that makes this sort of thing more easy. Using the sort method with a key selector, you can sort by birthDate as follows:

NSArray* sortedByBirthDate = [input sort:^id(id person) {
    return [person birthDate];
}]

@Peter Mortensen 2017-11-28 13:59:19

You ought to call it "LINQ to Objective-C".

@Emile Khattar 2013-01-10 15:37:39

-(NSMutableArray*) sortArray:(NSMutableArray *)toBeSorted 
{
  NSArray *sortedArray;
  sortedArray = [toBeSorted sortedArrayUsingComparator:^NSComparisonResult(id a, id b) 
  {
    return [a compare:b];
 }];
 return [sortedArray mutableCopy];
}

@vikingosegundo 2013-01-10 15:40:36

why to pass in a mutable array, when a new array is returned. why to create a wrapper at all?

@freespace 2009-04-30 06:20:00

Your Person objects need to implement a method, say compare: which takes another Person object, and return NSComparisonResult according to the relationship between the 2 objects.

Then you would call sortedArrayUsingSelector: with @selector(compare:) and it should be done.

There are other ways, but as far as I know there is no Cocoa-equiv of the Comparable interface. Using sortedArrayUsingSelector: is probably the most painless way to do it.

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