iphone - Sorting NSString values as if NSInteger using NSSortDescriptor

Question

I have created a sort descriptor to sort a plist response coming from my server. This works well with sort key having values upto 9. With more than 10 items I see abrupt results with sort key arranged in the order = 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"sort" ascending:YES];
self.myList = [NSMutableArray arrayWithArray:[unsortedList sortedArrayUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]]];

How to make it arrange in the correct order of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11?

Answer 1

You can do this by implementing a custom comparator block when creating your NSSortDescriptor:

NSSortDescriptor *aSortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"sort" ascending:YES comparator:^(id obj1, id obj2) {

    if ([obj1 integerValue] > [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedDescending;
    }
    if ([obj1 integerValue] < [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedAscending;
    }
    return (NSComparisonResult)NSOrderedSame;
}];
self.myList = [NSMutableArray arrayWithArray:[unsortedList sortedArrayUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]]];

See Apple documentation here