How to do sparse array in Cocoa

Question

I have an undetermined size for a dataset based on unique integer keys.

I would like to use an NSMutableArray for fast lookup since all my keys are inte

Answer 1

It sounds like your needs would be better met with an NSMutableDictionary. You will need to wrap the ints into NSNumber objects as follows:

-(void)addItem:(int)key value:(id)obj
{
    [data setObject:obj forKey:[NSNumber numberWithInt:key]];
}

-(id)getItem:(int)key
{
    return [data objectForKey:[NSNumber numberWithInt:key]];
}

There's no easy was to enlarge the size of an NSMutableArray, since you cannot have nil objects in the in-between slots. You can, however, use [NSNull null] as a 'filler' to create the appearance of a sparse array.