NSMutableArray subclass init

Question

I'm trying to make a function for a NSMutableArray subclass that only uses integer, but I don't want to use "count." How do I do this?

-(NSMutableArrayWithIntegers*)initWithCount:(NSInteger)count numbers:(NSInteger)firstInt, ...
{
    self = [super init];

    if (self) {
        va_list args;
        va_start(args, firstInt);
        NSInteger arg = firstInt;
        for (int i = 0; i < count; i++)
        {
            arg = va_arg(args, NSInteger);
            [self addObject: [NSNumber numberWithInteger:arg]];
        }
        va_end(args);
    }

    return self;
}

@trojanfoe I'm guessing he wants to use variable arguments but not have to specify the count as one of the arguments — David Rönnqvist
– David Rönnqvist, Commented Apr 3, 2013 at 13:47
For the love of everything holy don't subclass NSMutableArray — QED
– QED, Commented Apr 3, 2013 at 13:54
Yes, listen to @psoft. If you want to make a class that acts like a mutable array then I'd suggest using NSObject and giving it an NSMutableArray or adding a category to it. Whatever you do, do not subclass NSMutableArray. — Fogmeister
– Fogmeister, Commented Apr 3, 2013 at 14:06
For what you're doing you might have more luck just using an NSIndexSet, NSIndexPath or NSCountedSet. — iluvcapra
– iluvcapra, Commented Apr 3, 2013 at 14:23

QED · Accepted Answer · 2013-04-03 14:05:55Z

2

I know this doesn't answer your question but it's important to let you know. Don't ever subclass NSMutableAnything. Use a category and thank me later:

@interface NSMutableArray (ListOfIntegers)

+(NSMutableArray)mutableArrayWithIntegers:(NSInteger)i, ... {
   NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:whatever];
   // do your thing
   return array;
}

@end

answered Apr 3, 2013 at 14:05

QED

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1 Comment

Elliott Over a year ago

I don't doubt for a second that your point has merit but it would be nice if you could explain why subclassing NSMutableArray is undesirable?

score 0 · Accepted Answer · 2013-04-03 14:04:17Z

First of all, the approach you currently have is just fine. Don't try getting rid of the count. There are alternatives, but they are only worse.

For example, you may use a sentinel value (which may not be inserted into the array) as the last argument, but in this case, you will have to make sure that you are not actually trying to insert this value to the array at all:

- (id)initWithIntegers:(NSInteger)first, ...
{
    if (!(self = [super init])) return nil;

    va_list args;
    va_start(args, first);
    NSInteger n;
    if (first != NSIntegerMax) {
        [self addObject:@(first)];
        while ((n = va_arg(args, NSInteger)) != NSIntegerMax) {
            [self addObject:@(n)];
        }
    }

    va_end(args);

    return self;
}

But really, this unnecessarily narrows the range of values that can be added - using that count argument is not a big deal.

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