Sort an NSArray in Descending Order

Question

I have an NSArray of NSNumber objects that I have successfully sorted in ascending order using the following:

[myArray sortedArrayUsingSelector:@selector(compare:)]

However, I need to sort this in descending order. I take it that compare: only sorts in ascending order. While I can go about reversing the NSArray, I am curious as to whether or not there is a more simpler or more effective way of going about doing this.

EDIT: I found this question which provides a simple way to reverse iterate an NSArray:

for (id someObject in [myArray reverseObjectEnumerator])

This works fine, I guess it's a nice simple solution, but I'm curious as to whether or not there is a way to specify sorting in descending order.

Answer 1

Use a sort descriptor

NSSortDescriptor* sortOrder = [NSSortDescriptor sortDescriptorWithKey: @"self" 
                                                            ascending: NO];
return [myArray sortedArrayUsingDescriptors: [NSArray arrayWithObject: sortOrder]];

Answer 2

Another way, imo, is also nice: write another reverseCompare with category:

@implementation NSNumber (Utility)

- (NSComparisonResult)reverseCompare:(NSNumber *)aNumber {
  return [aNumber compare:self];
}

The good thing is that you can reuse everywhere and don't have to write the loop with reverse iterate. The bad thing is that you have to write more code:)

Answer 3

use sortarrayusingcomparator method like that

NSArray *sortedArray = [array sortedArrayUsingComparator:
^NSComparisonResult(id obj1, id obj2){
        return [obj2 compare:obj1];
    }];

by reversing the order of objects you will obtain a descending order