Sorting array of dictionaries by number

Question

So I have an array with about 180 dictionaries, There are 5 objects in each dictionary (3 strings and 2 NSNumbers)

I am trying to sort each dictionary by one of its properties, this works fine for the strings but when it comes to the number it does not sort correctly.

 -(void) sortArrayBy:(int)sortingNumber {

    switch (sortingNumber) {
            case 0:
                NSLog(@"sorting by atomicnumber");
                [self.elementsArray sortUsingDescriptors:[NSArray arrayWithObjects:
 // When sorting this comes back the same each time but not in the correct order
                [NSSortDescriptor sortDescriptorWithKey:@"ATOMIC NUMBER" ascending:YES], nil]];
                break;
            case 1:
                NSLog(@"sorting by name");
                [self.elementsArray sortUsingDescriptors:[NSArray arrayWithObjects: [NSSortDescriptor sortDescriptorWithKey:@"ELEMENT NAME" ascending:YES], nil]];
                break;
            case 2:
                NSLog(@"sorting by symbol");
                [self.elementsArray sortUsingDescriptors:[NSArray arrayWithObjects: [NSSortDescriptor sortDescriptorWithKey:@"CHEMICAL SYMBOL" ascending:YES], nil]];
                break;
            case 3:
                NSLog(@"sorting by mass");
 // When sorting this comes back the same each time but not in the correct order
                [self.elementsArray sortUsingDescriptors:[NSArray arrayWithObjects: [NSSortDescriptor sortDescriptorWithKey:@"ATOMIC MASS" ascending:YES], nil]];
                break;

            default:
                break;
        }

Care to clarify "consistent but not correct", please? '1, 20, 3', for example, is "constitent and correct" for certain applications. — Jongware
– Jongware, Commented Jul 29, 2013 at 9:39
Could you give an example of "consistent but incorrect" sorting? Show us a sub-sequence after the sort, and point out the out-of-order items. — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jul 29, 2013 at 9:39
I mean each time I sort it it comes back the same but the order is incorrect — flux
– flux, Commented Jul 29, 2013 at 9:40
@user2113952 Is there any pattern to that incorrect order, though? Could you show, say, the first ten..fifteen numbers after the sort? — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jul 29, 2013 at 9:44

flux · Accepted Answer · 2013-07-29 10:09:23Z

4

Ok so I figured out the problem, it was sorting by the first number not the whole number for some reason, so i use this code:

        NSSortDescriptor *sortDescriptor = [NSSortDescriptor 

sortDescriptorWithKey:@"ATOMIC MASS" ascending:YES comparator:^(id obj1, id obj2) {
                return [obj1 compare:obj2 options:NSNumericSearch];
            }];

            [self.elementsArray sortUsingDescriptors:[NSArray arrayWithObjects: sortDescriptor, nil]];

answered Jul 29, 2013 at 10:09

flux

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2 Comments

Hot Licks Over a year ago

It was sorting the numbers "alphabetically", meaning that 100 will sort before 2.

Jongware Over a year ago

That is exactly what my comment inferred. A short example list of 'badly sorted' data would have shown it immediately.

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