Objective C - NSMutableSet not working properly - objective-c

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];
}