Question

I have a synthesized NSMutableArray – theResultArray . I want to insert NSNumber or NSInteger objects at specific indexes (0-49). For some reason I can never get any values to stick in my array. Every index returns nil or 0.

    NSInteger timeNum = time;
    [theResultArray insertObject:[NSNumber numberWithInt:timeNum] atIndex:rightIndex];
    NSLog(@"The right index is :%i", rightIndex);
    NSLog(@"The attempted insert time :%i", time);
    NSNumber *testNum = [theResultArray objectAtIndex:rightIndex];
    NSLog(@"The result of time insert is:%i", [testNum intValue]);

I alloc-init theResultsArray in viewDidLoad. Time is an integer. I have been trying different combinations of the code above to no avail.

The console outputs this:

StateOutlineFlashCards[20389:20b] The right index is :20
StateOutlineFlashCards[20389:20b] The attempted insert time :8
StateOutlineFlashCards[20389:20b] The result of time insert is:0

Answer 1

You need to allocate memory for the array in your init or viewDidLoad method, otherwise you won’t be able to store anything at all.

If you do this:

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
        // Custom initialization        
        myMutableArrayName = [[NSMutableArray alloc] init];
    }
    return self;
}

Or this:

- (void)viewDidLoad {
    [super viewDidLoad];
    myMutableArrayName = [[NSMutableArray alloc] init];
}

It should work for you.

As for storing integers in an NSMutableArray, I took a simple but somewhat “hackish” approach recently. I store them as strings. When I put them in I use:

[NSString stringWithFormat:@"%d", myInteger];

And when I take them out I convert with:

[[myArray objectAtIndex:2] intValue];

It was really easy to implement but depending on the context you may want to use another way.