Question

Following the StringCalculator kata from Xcode Katas, I ended up with a following class.

@implementation StringCalculator

- (int) add: (NSString *) string {    
    // this is marked as a potential memory leak by the `Analyze` tool
    NSMutableString *separatorCharacters = [@"\n" mutableCopy];

    if ([string hasPrefix:@"//"]) {
        NSRange range = NSMakeRange(2, 1);
        NSString *additionalSeparator = [string substringWithRange:range];
        [separatorCharacters appendString:additionalSeparator];
    } else {
        [separatorCharacters appendString:@","];
    }

    NSCharacterSet *separators = [NSCharacterSet characterSetWithCharactersInString:separatorCharacters];
    NSArray *numbers = [string componentsSeparatedByCharactersInSet:separators];

    // [separatorCharacters release];

    int sum = 0;    
    for (NSString *number in numbers) {
        sum += [number intValue];
    }
    return sum;
}

@end

Everything works fine, but when I run Analyze, I’m getting a potential memory leak on the first line of the method. If I do a manual release at the end, it seems to satisfy the analyzer, but I don’t really understand why this is happening.

How does creating a mutableCopy differ from a substringWithRange, for example? I’m not sure how to check if I’m using ARC, but if I wasn’t, I should be leaking memory on every single line where I create a object right?

I also thought that calling release is kind of deprecated or unnecessary in ARC projects.

Answer 1

If I do a manual release at the end, it seems to satisfy the analyzer

You aren’t using ARC. Manual releasing is forbidden with ARC, this wouldn’t compile. Check your build settings.