Sorting objects in NSMutableArray with sortUsingComparator

Question

I have the following mutable array:

NSMutableArray *persons = [[NSMutableArray alloc]initWithObjects:person1, person2, person3, nil];

where every person is an object, which contains (NSInteger) personAge and (NSString*) personName properties. Now I want to sort this array by personAge. So I tried the following:

[persons sortUsingComparator:
     ^NSComparisonResult(id obj1, id obj2)
     {
         Person *p1 = (Person*)obj1;
         Person *p2 = (Person*)obj2;

        return [p1.personAge compare: p2.personAge];

     }];

    NSLog(@"%ld", [persons componentsJoinedByString:@" "]);

But I'm getting a "Bad receiver type 'NSInteger' (aka 'long')" error message in the return line. Also I have a warning in the NSLog line: "Format specifies type 'long' but the argument has type 'NSString *'". How do I fix it?

Iulian Onofrei · Accepted Answer · 2022-04-20 14:23:12Z

39

Shouldn't you use something like this instead?

[persons sortUsingComparator:
    ^NSComparisonResult(id obj1, id obj2) {
        Person *p1 = (Person*)obj1;
        Person *p2 = (Person*)obj2;

        if (p1.personAge > p2.personAge) {
            return (NSComparisonResult)NSOrderedDescending;
        }

        if (p1.personAge < p2.personAge) {
            return (NSComparisonResult)NSOrderedAscending;
        }

        return (NSComparisonResult)NSOrderedSame;
    }
];

The thing is that you have rely on the compare method which doesn't exist on NSInteger: it is only a typedef of int. So you want to compare integer value instead and returns an NSComparisonResult value to denote the ordering of your object accordingly.

edited Apr 20, 2022 at 14:23

Iulian Onofrei

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answered Sep 11, 2012 at 13:01

tiguero

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13 Comments

Igal Over a year ago

Yep, same result as in the above answer: <Person: 0x10010a720> <Person: 0x10010ad20> <Person: 0x100108ab0> And the same question: Is there any way that instead of Person: xxxxxxx I would get the actual personAge? So it would look something like that: 1, 27, 34 etc..?

tiguero Over a year ago

[p1.personAge intValue] I think you are printing your NSNumber object

Igal Over a year ago

OK, I'm confused now... Did you mean I should do something like that:

if ([p1.personAge intValue] > [p2.personAge intValue]) {                  return (NSComparisonResult)NSOrderedDescending;              }

? Then I'm still getting the "Bad receiver..." error. Still have no idea how to print the age of each person...

tiguero Over a year ago

Sorry if i wasn't clear you just need to do a NSLog with the right format: NSLog(@"Age: %d", p1.personAge)

tiguero Over a year ago

forget about my comment with the NSNumber object, you are using NSInteger, it is a typedef of an integer

|

Wevah · Accepted Answer · 2012-09-11 13:02:34Z

4

You're trying to call compare: on an NSInteger, which is not an object; it's a typedef for an integer type (either int or long depending on architecture).

Also, componentsJoinedByString: returns an NSString, not an integer.

Try:

[persons sortUsingComparator:
    ^NSComparisonResult(id obj1, id obj2)
    {
        Person *p1 = (Person*)obj1;
        Person *p2 = (Person*)obj2;

        if (p1.personAge < p2.personAge)
            return NSOrderedAscending;
        if (p1.personAge > p2.personAge)
            return NSOrderedDescending;
        return NSOrderedSame;
 }];

NSLog(@"%@", [persons componentsJoinedByString:@" "]);

answered Sep 11, 2012 at 13:02

Wevah

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3 Comments

Igal Over a year ago

I tried it and I got this result: <Person: 0x10010a720> <Person: 0x10010ad20> <Person: 0x100108ab0> Is there any way that instead of Person: xxxxxxx I would get the actual personAge? So it would look something like that: 1, 27, 34 etc..?

Wevah Over a year ago

[[persons valueForKey:@"personAge"] componentsJoinedByString:@" "]

rdelmar Over a year ago

@Igal, you could also write a description method in your Person class, so that when you do NSLog(@"%@",aPerson), you get something like: "name:Bill, age:26" instead of <Person: 0x10010a720>.

jrtc27 · Accepted Answer · 2012-09-11 13:04:18Z

1

Regarding the "Bad receiver type..." error, NSInteger is a primitive data type (not an Objective-C class) so you can't call methods on it. what you want to do is the following:

if (p1.personAge > p2.personAge) {
    return (NSComparisonResult)NSOrderedDescending;
}

if (p1.personAge < p2.personAge) {
    return (NSComparisonResult)NSOrderedAscending;
}
return (NSComparisonResult)NSOrderedSame;

The warning is due to the fact that @"%ld" is the format string for a long (as the warning says), but -componentsSeparatedByString: returns an NSString object. The correct format string for any Objective-C object is @"%@", so the line should read NSLog(@"%@", [persons componentsJoinedByString:@" "]);.

answered Sep 11, 2012 at 13:04

jrtc27

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2 Comments

Igal Over a year ago

Is there any way that I could get the actual personAge? So it would look something like that: 1, 27, 34 etc.. instead of Person: xxxxxxx in the result?

jrtc27 Over a year ago

Easiest way is to override the -description method in your Person class to return what you want it to display as.

malhal · Accepted Answer · 2014-02-02 01:21:41Z

0

Like tigeguero's answer but tidier:

 [people sortUsingComparator:
      ^NSComparisonResult(Person* p1, Person* p2){

            if (p1.personAge > p2.personAge) {
                return NSOrderedDescending;
            }
            else if (p1.personAge < p2.personAge) {
                return NSOrderedAscending;
            }
            else{
                return NSOrderedSame;
            } 
    }
 ];

answered Feb 2, 2014 at 1:21

malhal

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Comments

Hiren · Accepted Answer · 2015-10-28 08:23:38Z

0

[YOURMutableArray sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

edited Oct 28, 2015 at 8:23

Hiren

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answered Feb 20, 2013 at 9:59

Amit Singh

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1 Comment

JAL Over a year ago

While this may in fact answer the question, can you elaborate on what this code actually does?

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