Question

Good evening.

This code works. It sorts an array of cards by both Suit and Card Value. It is also very much brute force. Can you recommend a better way? Does Objective-C help dealing with a situation where object being sorted itself has multiple fields, on which sorting depends?

-(void) sort: (NSMutableArray *) deck {        
    NSUInteger count = [deck count];

    Card *thisCard;
    Card *nextCard;

    int this;
    int next;

    BOOL stillSwapping = true;

    while (stillSwapping) {

        stillSwapping = false;

        for (NSUInteger i = 0; i < count; ++i) {
            this = i;
            next = i+1;

            if (next < count) {

                thisCard = [deck objectAtIndex:this];
                nextCard = [deck objectAtIndex:next];

                if ([thisCard suit] > [nextCard suit]) {                        
                    [deck exchangeObjectAtIndex:this withObjectAtIndex:next];
                    stillSwapping = true;
                } 


                if ([thisCard suit] == [nextCard suit]) {
                    if ([thisCard value] > [nextCard value]) {
                        [deck exchangeObjectAtIndex:this withObjectAtIndex:next];
                        stillSwapping = true;
                    } 
                }
            }
        }
    }
}

Answer 1

You have several options.

Perhaps the simplest is to define the method -compare: on Card, which returns an NSComparisonResult. This is preferable if sorting by suit and value is the “standard” way to sort a Card. If you’ve done this, then your entire sorting method can be turned into

[deck sortUsingSelector:@selector(compare:)];

If you don’t want to do this, you can use an array of NSSortDescriptors, one for suit and one for value.

[deck sortUsingDescriptors:[NSArray arrayWithObjects:[NSSortDescriptor sortDescriptorWithKey:@"suit" ascending:YES], [NSSortDescriptor sortDescriptorWithKey:@"value"] ascending:YES], nil]];

If this doesn’t work for whatever reason, you could try -sortUsingComparator:

[deck sortUsingComparator:^NSComparisonResult(Card *obj1, Card *obj2) {
    int suit1 = [obj1 suit];
    int suit2 = [obj2 suit];
    if (suit1 > suit2) {
        return NSOrderedDescending;
    } else if (suit1 < suit2) {
        return NSOrderedAscending;
    } else {
        id value1 = [obj1 value];
        id value2 = [obj2 value];
        if (value1 > value2) {
            return NSOrderedDescending;
        } else if (value1 < value2) {
            return NSOrderedAscending;
        } else {
            return NSOrderedSame;
        }
    }
}