Static Variable in Cocoa Class Category

Question

I have a cocoa 'category' for adding inflections (pluralize, singularize, etc.) to NSString. The code requires loading a set of regular expression rules and exceptions from a PLIST into dictionaries and arrays, as well as adding manual exceptions from code. I need a way to persist these data structures (as class members) between multiple calls to the inflection code (all instance methods). I attempted:

+ (NSMutableArray *)uncountables 
{
    static NSMutableArray *uncountables = nil;
    if (uncountables == nil) uncountables = [NSMutableArray array];
    return uncountables;
}

However, it appears to fail occasionally. Does a good way of doing this exist? I don't want to subclass NSString if possible. Thanks.

Answer 1

I think this code is OK. I use the same thing a lot for singletons. But be aware that it is not thread safe this way. Maybe you calling it from different threads?

Answer 2

[NSMutableArray array];

returns an autoreleased array. Use this instead:

[[NSMutableArray alloc] init];

Answer 3

As drawnonward already mentioned, [NSMutableArray array]; returns an autoreleased array. But I don't think, it's a good idea to return non-autoreleased array, because it contradicts with Cocoa memory management conceptions - only alloc, copy and new should be released manually. All other initializations are autoreleased.

So, you should just use

interface:
NSArray *a;

...somewhere in a code...
a = [[NSString uncountables] retain];
...

- (void)dealloc {
    [a release];
}

to get properly retained/released objects.