Question

I have two arrays, both full of NSString objects like this:

NSMutableArray *titles = [[NSMutableArray alloc] initWithObjects:@"Title1", @"Title2", @"Title3", @"Title4", @"Title5", nil];

NSMutableArray *distances = [[NSMutableArray alloc] initWithObjects:@"139.45", @"23.78", @"347.82", @"10.29", @"8.29", nil];

How can I sort both arrays by the nearest distance first?

So the results would be like this:

titles = @"Title5", @"Title4", @"Title2", @"Title1", @"Title3"
distances = @"8.29", @"10.29", @"23.78", @"139.45", @"347.82"

I understand that NSSortDescriptor can be used in these circumstances but after looking through the documentation, I am still unsure about how.

Answer 1

I would sort the distances this way…

NSNumberFormatter *f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterDecimalStyle];

NSArray *sortedDistances = [listItem sortedArrayUsingComparator: ^(id a, id b) {
    NSNumber *aNum = [f numberFromString:a];
    NSNumber *bNum = [f numberFromString:b];
    return [aNum compare:bNum];
}];

I can’t think of a particularly quick way to get the associated titles sorted, but this should work …

NSMutableArray *sortedTitles = [NSMutableArray array];
NSDictionary *distanceTitle = [NSDictionary dictionaryWithObjects:titles forKeys:distances];

for (NSString *distance in sortedDistances) {
    NSString *associatedTitle = [distanceTitle valueForKey:distance];
    [sortedTitles addObject:associatedTitle];
}