objective-C, sort an array of strings containing numbers [duplicate]

Question

Lets suppose I have an array like this

NSArray* arr = @[@"1",@"4",@"2",@"8",@"11",@"10",@"14",@"9"]; //note: strings containing numbers

and I want to sort them like this: [1,2,4,8,9,10,11,14]

but if I use

[arr sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

I get [1,10,11,14,2,4,8,9]... and if I use:

   NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"length" ascending:YES];
   NSArray *sortDescriptors = @[sortDescriptor];
   [arr sortedArrayUsingDescriptors:sortDescriptors];

I get something like this: [1,4,2,8,9,11,10,14]

How can I combine both predicates? or is any other easier way to solve this? note: The output of this array is merely for debug purposes, I dont care if the result turns the array into integers as long as I can print in console with NSLog thanks

Answer 1

The problem is that you're trying to use both string comparison and -length to cobble together what you really want, which is numeric comparison. But sort descriptors are applied one at a time, and a second descriptor is only used if the first one orders two items as the same. Using -intValue to order the items lets you use a single sort descriptor that will order the items the way you want.

Do this instead:

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"intValue" ascending:YES];
[arr sortedArrayUsingDescriptors:@[sortDescriptor]];