Static analyzer says I have the potential leak of an object...

Question

This is an object I made to do some flash cards. The first method (I left out the main part) generates a NSMutabaleArray of Card objects with the passed in operator and works fine. The second method, "drawFromDeck" gets called on a Deck object from my view controller and also works fine, but the Static Analyzer says I may be leaking an object.

Here is the code.

#import "Deck.h"

@class Deck;
@implementation Deck

@synthesize cards;

- (id)initDeckWithOperator: (NSString*)mathOper {

...

 return self;
}

- (id)drawFromDeck {
    int index = random() % [cards count];
    Card* selectedCard = [[cards objectAtIndex:index] retain];
    [cards removeObjectAtIndex:index];
    return selectedCard;
}

@end

Answer 1

Yes you're leaking an object. You should

return [selectedCard autorelease];

The reason being you've -retained the selectedCard, so you've got the responsibility to -release it. But you can't use -release since it must be valid after the function ends, so you need to use -autorelease to transfer the ownership to the auto-release pool.

Of course, methods calling -drawFromDeck shouldn't -release its return value.

Answer 2

Thanks for the input. I didn't used to have the retain in there, but I would end up crashing for index being out of bounds of the array. I tried doing the autorelease thing, but I would crash then too - but like you said, I don't want to release that selectedCard because I need to use it when it gets back to my ViewController. I don't recall if I release it when I'm done with it in the ViewController, but would that work? Would the SA know that even though I return an object with a +1 retain count, that it gets released in the ViewController?