How can I declare and initialize a n° of variables without knowing how many are?

Question

Let me explain what I mean:

I need to declare and init a number x of SKNode variables (between 1 and 15) based on which value is passed through the method:

- (instancetype)initWithNumberOfNodes:(int)number;

Every SKNode will be added into a NSMutableArray so I won't have problem with references (I will get every single items with [myArray objectAtIndex:]). I don't think that create 15 SKNode variables could be the best solution due to the large wasting of memory and an odd programming style.

Any clues?

Answer 1

If you know you're going to need 15, or whatever number is, you can store that in a property:

@property (nonatomic, assign) NSUInteger number;

- (instancetype)initWithNumberOfNodes:(int)number {
    // ... normal stuff ...

        self.number = number;
        self.nodes = [NSMutableArray arrayWithCapacity:number];

        // Populate with placeholders to avoid out of bounds access later.
        for (int i = 0; i < number; ++i) { 
            self.nodes[i] = [NSNull null];  
        }

    // ... normal stuff ...
}

Then, write yourself a little helper to lazily create them.

- (SKNode*)nodeAtIndex:(NSUInteger)index {
    NSAssert(index < self.number, @"bad index");

    SKNode* node = [self.nodes objectAtIndex:index];
    if ([node isKindOfClass:[NSNull class]]) {
        node = [[SKNode alloc] init];  // Or whatever.
        [self.nodes replaceObjectAtIndex:index withObject:node];
    }
    return node;
}

And use your helper whenever you need a node:

SKNode* someNode = [self nodeAtIndex:someIndex];