Question

I know this is fairly fundamental stuff.

I have a class with a function that returns the name of the month; I’m not sure how to release a value that I want to return to prevent leaks.

In the class this value is declared:

static NSDateFormatter *formatter = nil;
if (formatter == nil) {
    formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"MMMM yyyy"];
}

Things happen, and then:

if([exampleDate isEqualToDate:
    [[self creationDate] laterDate:exampleDate]])
{ //earlierDate returns the earlier date
    return(@"Examples");
}else{
    return([formatter stringFromDate:[self creationDate]]);
}

I’ve tried using autorelease but I’m using it incorrectly because I get a crash when I try to release it. I’ve also tried assigning the return value to a string, but I have the same crashing problems. Sorry for asking a question that is so fundamental, but I’d appreciate knowing how to release this properly, while still returning the value – and understanding how it works.

Answer 1

there are no leaks in the return part. Since stringFromDate: is not copy, mutableCopy, retain, alloc or new it returns already an autoreleased object.

Your NSDateFormatter will leak when the class is deallocated. If you don’t want it to leak you should create a @property for it and release it in dealloc.
Local static objects will always leak.
I would not use such objects outside of singletons. Each time you create one of your classes you will leak an NSDateFormatter. Using @property is better in almost every case.

I’ve seen hacks like this but in my opinion they solve a problem you shouldn’t have in the first place:

- (NSString *)someDateFromString:(NSString *)str {
    static NSDateFormatter *formatter = nil;
    if (formatter == nil) {
        formatter = [[NSDateFormatter alloc] init];
    }
    if (str == nil) {
        [formatter release];
        formatter = nil;
        return nil;
    }
    // do something
    return date;
}

- (void)dealloc {
    [self someDateFromString:nil]; // will release the static date formatter.
    [super dealloc];
}