Question

I eliminated all the leaks from my current app. However Instruments constantly tells me that I have a leak in the method shown below.

The leak is of type NSMutableArray and has a size of either 16 or 32 bytes. Yes, I know that’s not much but it adds up. Also see it as an academic question that I need to solve to make my code leakless.

+ (id) meterFromDict:(NSDictionary*)dict {
    Meter* resMeter = [[Meter alloc] initWithType:[[dict objectForKey:@"MeterBase"] intValue]];
    //NSLog(@"dict: %@",dict);
    resMeter.volume = nil;
    resMeter.sounds = nil;
    resMeter.repeats = nil;

    resMeter.volume = [[[NSMutableArray alloc] initWithArray:[dict objectForKey:@"volumeArray"]] autorelease];
    resMeter.sounds = [[[NSMutableArray alloc] initWithArray:[dict objectForKey:@"soundsArray"]] autorelease];
    resMeter.repeats = [[[NSMutableArray alloc] initWithArray:[dict objectForKey:@"repeatsArray"]] autorelease];
    //NSLog(@"MeterFromDict called and resmeter.repeats count is : %i",[resMeter.repeats count]);
    resMeter.bpm = [[dict objectForKey:@"BPM"] floatValue];

    return [resMeter autorelease];
}

Answer 1

Without looking at your Instruments output directly I can’t tell exactly, but you’re writing some redundant code: Try this:

+ (id) meterFromDict:(NSDictionary*)dict {
    Meter* resMeter = [[Meter alloc] initWithType:[[dict objectForKey:@"MeterBase"] intValue]];
    //NSLog(@"dict: %@",dict);

    resMeter.volume = [dict objectForKey:@"volumeArray"];
    resMeter.sounds = [dict objectForKey:@"soundsArray"];
    resMeter.repeats = [dict objectForKey:@"repeatsArray"];
    //NSLog(@"MeterFromDict called and resmeter.repeats count is : %i",[resMeter.repeats count]);
    resMeter.bpm = [[dict objectForKey:@"BPM"] floatValue];

    return [resMeter autorelease];
}

There’s no point in nilling your properties before assigning new values to them.

Also, No point creating new arrays for arrays that you already have. And if you have properly declared your volume, sounds and repeats properties with copy instead of retain.

Try that and see if it works better.