Question

I have code that returns an NSComparisonResult. My codes works great for sorting my arrays in Ascending and Descending order when they are NSStrings with only alphabetic characters in them.

When the NSStrings have numbers in them, such as Seinfeld (Season 5) and Seinfeld (Season 6) they are sorting correctly Ascending in the order of 5 and then 6. But Descending it still sorts it as 5 and 6. Here’s an example:

Ascending:
Batman,
Seinfeld (Season 5),
Seinfeld (Season 6),
Zoolander

Descending:
Zoolander,
Seinfeld (Season 5),
Seinfeld (Season 6),
Batman

The descending code I have looks like this to return the comparison:

return [(NSString *)secondString compare:(NSString *)firstString options:NSNumericSearch];

Any ideas on how to reverse NSStrings with numbers in them?

By the way, I can’t use NSSortDescriptor in my case. The code I have requires a custom function to be built because I have to do some string appending, etc, before the sort occurs. I didn’t include it all for simplicity.

Answer 1

Essentially the same comment as above, but here’s full source and output to prove it works (iOS 4.3 simulator tested):

NSArray * strings = [NSArray arrayWithObjects: @"Seinfeld (Season 6)", @"Batman", @"Seinfeld (Season 5)", @"Zoolander", nil];
NSArray * sorted1 = [strings sortedArrayUsingComparator: ^(id first, id second) {
                        return [(NSString *)first compare:(NSString *)second options: NSNumericSearch];
                    }];
NSArray * sorted2 = [strings sortedArrayUsingComparator: ^(id first, id second) {
    return - [(NSString *)first compare:(NSString *)second options: NSNumericSearch];
    // or (to be more clear, but less efficient)
    // return -1 * [(NSString *)first compare:(NSString *)second options: NSNumericSearch];
}];

NSLog(@"starting: %@", strings );
NSLog(@"sort1: %@", sorted1 );
NSLog(@"sort2: %@", sorted2 );

output:

2011-10-19 02:09:07.557 test2222[16793:207] starting: (
  "Seinfeld (Season 6)",
  Batman,
  "Seinfeld (Season 5)",
  Zoolander
)

2011-10-19 02:09:07.558 test2222[16793:207] sort1: (
  Batman,
  "Seinfeld (Season 5)",
  "Seinfeld (Season 6)",
  Zoolander
)

2011-10-19 02:09:07.558 test2222[16793:207] sort2: (
  Zoolander,
  "Seinfeld (Season 6)",
  "Seinfeld (Season 5)",
  Batman
) 

---

In answer to Ethan Allen, here’s the output for a test with numbers in front:

2011-12-14 21:01:26.535 Test[7475:f803] starting: (
    "2001 Seinfeld (Season 6)",
    "1999 Batman",
    "2112 Seinfeld (Season 5)",
    "10 Zoolander"
)
2011-12-14 21:01:26.537 Test[7475:f803] sort1: (
    "10 Zoolander",
    "1999 Batman",
    "2001 Seinfeld (Season 6)",
    "2112 Seinfeld (Season 5)"
)
2011-12-14 21:01:26.537 Test[7475:f803] sort2: (
    "2112 Seinfeld (Season 5)",
    "2001 Seinfeld (Season 6)",
    "1999 Batman",
    "10 Zoolander"
)