Question

I have this method:

-(NSString *)scrambleWordGenerator: (NSUInteger)length {
    NSMutableString *scrambledWord = [[NSMutableString alloc] initWithString:@""];
    for (int i = 0; i < length; i++) {
        NSUInteger randomIndex = arc4random() % [self.arrayOfCharacters count];
        NSString *randomCharacter = [NSString stringWithString:[self.arrayOfCharacters objectAtIndex:randomIndex]];
        [scrambledWord insertString:randomCharacter atIndex:i];
    }
    NSString *finalWord = [[NSString alloc] initWithString:scrambledWord];
    [scrambledWord release];
    return finalWord;
}

It works, swimmingly in fact, however upon using Xcode’s “Analysis” feature, it says that finalWord has a potential memory leak.

I thought when creating a NSString with a prefab init method that the string will be autoreleased. What am I missing? Below is a screen grab of the error:

edit

The method now looks like this:

-(NSString *)scrambleWordGenerator: (NSUInteger)length {
    NSMutableString *scrambledWord = [[NSMutableString alloc] initWithString:@""];
    for (int i = 0; i < length; i++) {
        NSUInteger randomIndex = arc4random() % [self.arrayOfCharacters count];
        NSString *randomCharacter = [NSString stringWithString:[self.arrayOfCharacters objectAtIndex:randomIndex]];
        [scrambledWord insertString:randomCharacter atIndex:i];
    }
    NSString *finalWord = [NSString stringWithString:scrambledWord];
    [scrambledWord release];
    return finalWord;
}

And no more errors!

Answer 1

No, the moment you use alloc, you’re responsible for releasing it – either by release or by moving it to autorelease pool via autorelease.

It would be on the autorelease pool if you used [NSString stringWithString:] instead.