Objective C - NSMutableSet not working properly

Question

I have an NSMutableSet that I am trying to add labels to. After each label added, I check the set's count and it comes back as 0. Any help will be appreciated

In my .h file:

@interface MainMenu : CCLayerColor {
    NSMutableSet* letters;
}

In my .m file:

-(void)initiateLetters{
    //Grab the window size
    CGSize size = [[CCDirector sharedDirector] winSize];

    int i;
    for(i=0;i<100;i++){
        CCLabelTTF *label;
        int r = rand() % 35 + 60;
        char c = (char) r;
        label = [CCLabelTTF labelWithString:[NSString stringWithFormat:@"%c",c] fontName:@"Courier" fontSize:30];
        [label setColor:ccc3(0,0,0)];
        [label setOpacity:255/2];

        //Generate a random number for the x variable, y will be 0
        int x = (arc4random() % (int)size.width);
        int y = size.height+(arc4random() % 50)+25;

        [label setPosition:ccp(x,y)];
        [self addChild:label];
        [letters addObject:label];

        //Here's what's printing 0:
        printf("%lu",[letters count]);
    }
}

Answer 1

You have to instantiate the set before you can add things to it. You can do that in an overridden implementation of init:

- (id)init
{
    self = [super init];
    if (self) {
        letters = [[NSMutableSet alloc] init];
    }
    return self;
}

…or at the beginning of your initiateLetters method:

- (void)initiateLetters
{
    letters = [[NSMutableSet alloc] init];
    ...

Instead, the code you posted is simply sending addObject: to nil, which does nothing.

Answer 2

the array is probably nil. Did you create it in the class init method ?

something like

-(id) init { 

    if (self = [super init]){
        // ...
        letters = [[NSMutableSet set] retain];   // not using ARC
        // ...
    }
    return self;
}

and of course

-(void) dealloc {

    // ...
    [letters release];              // not using ARC
    [super dealloc];    
}