Instruments says I have a memory leak, but I don't see it

Question

I have a method to generate a Deck object (NSObject subclass with an NSMutableArray property) and it populates the array with Card objects (UIView subclass with some integer and one NSString property). When I ask for a Deck I check to see if one already exists (I think) and if so, release it before getting a new one.

The code from my viewcontroller...

#import "FlashTestViewController.h"

@implementation FlashTestViewController

- (IBAction)generateDeck {

    if (aDeck != nil) {
        [aDeck release];
    }

    aDeck = [[Deck alloc] initDeckWithOperator:@"+"];
}


- (IBAction)generateCard {

    if (aCard != nil) {
        [aCard fadeAway];
    }

    aCard = [aDeck newCardFromDeck];
    [self.view addSubview:aCard];
}

- (void)fadeAway {
    [aCard removeFromSuperview];
    [aCard release];
    }

    @end

---

The Deck class is as follows...

#import <Foundation/Foundation.h>
#import "Card.h"

@class Deck;

@interface Deck : NSObject {

    NSMutableArray* cards;
}

@property(nonatomic, retain) NSMutableArray* cards;

- (id)initDeckWithOperator: (NSString*)mathOper;
- (id)newCardFromDeck;

@end

---

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

    if (cards != nil) {
        [cards release];
    }
    cards = [[NSMutableArray alloc] init];
    for (int i=0; i<11; i++) {
        for (int j=0; j<11; j++) {
            int xPos = (random() % 220) + 10;
            int yPos = (random() % 360) + 10;
            Card* aCard = [[Card alloc] initWithFrame:CGRectMake(xPos, yPos, 60, 80)];
            aCard.upperOperand = i;
            aCard.lowerOperand = j;
            aCard.theOperator = mathOper;
            aCard.theResult = i + j;

            UITextView* upperTextView = [[UITextView alloc] initWithFrame:CGRectMake(5, 5, 50, 20)];
        NSString* upperOper = [[NSString alloc] initWithFormat:@"     %d", i];
        upperTextView.text = upperOper;
        [aCard addSubview:upperTextView];
        [upperTextView release];
        [upperOper release];

        UITextView* middleTextView = [[UITextView alloc] initWithFrame:CGRectMake(5, 30, 50, 20)];
        NSString* middleOper = [[NSString alloc] initWithFormat:@"%@  %d", mathOper, j];
        middleTextView.text = middleOper;
        [aCard addSubview:middleTextView];
        [middleTextView release];
        [middleOper release];

        UITextView* lowerTextView = [[UITextView alloc] initWithFrame:CGRectMake(5, 55, 50, 20)];
        NSString* lowerOper = [[NSString alloc] initWithFormat:@"     %d", j+i];
            lowerTextView.text = lowerOper;
            [aCard addSubview:lowerTextView];
            [lowerTextView release];
            [lowerOper release];

            [cards addObject: aCard];
            [aCard release];
        }
    }
    return self;
}

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

@end

---

I do the same thing when I ask for a new card from the newCardFromDeck method and it works. Any suggestions?

Thanks!

Answer 1

Looking at this line of code:

cards = [[NSMutableArray alloc] init];

Do you release cards in your dealloc method? It looks like this could potentially be a memory leak.

Answer 2

Are you releasing 'cards'?

Answer 3

Add this code to your Deck.m file:

- (void)dealloc
{
    [cards release];
    [super dealloc];
}

Answer 4

aDeck in generateDeck is also be a leak if you don't release it in the view's dealloc.

Answer 5

In newCardFromDeck:

Card* selectedCard = [[cards objectAtIndex:index] retain];

looks like you retain the card and return it somewhere. Where does this return value end up? If it ends up in another variable with a 'retain' property on it, it can get retained a second time (upon assignment to the variable).