Question

I have

@interface PlayerDeck : Deck
@interface MasterDeck : Deck

Both PlayerDeck and MasterDeck have

@property (nonatomic, strong) NSMutableArray *cards;   // All cards in this Deck

Inside Deck’ I’d like to

-(NSString*) descriptionOfDeck: (Deck *) deck

Inside both PlayerDeck and MasterDeck i’d like to

-(NSString*) description{
    [super descriptionOfDeck:self];
}

Inside Deck i will iterate over cards inside each individual Decks:

-(NSString*) descriptionOfDeck: (Deck *) deck {

    NSString *deckDescription = [[NSString alloc] init];

    for (Card *c in [deck cards]) {
        deckDescription = [deckDescription 
                 stringByAppendingString:[c description]];
    }

    return deckDescription;
}

The problem: [deck cards] does not resolve.

Please help me understand.

Answer 1

If I understand correctly, you’re saying the cards property is only defined on the MasterDeck and PlayerDeck classes, and not on Deck.

If that’s correct, consider the type of deck when you attempt to send it the cards message: it is of type Deck, which doesn’t define cards. You need to either cast it to a type which does define cards, or define cards in the base class directly. The latter seems more sensible, both for resolving this issue, and because it seems appropriate that all Decks have cards!

Update: An example of casting in your case would be:

for (Card *c in [((MasterDeck *) deck) cards])

But you can see the problem with that, can’t you? It requires the base class to somehow know about its child classes, which sort of defeats the purpose of inheritance.

As I – and @rgeorge, in the comments – have suggested, declaring the cards property in the base class is the better move.