Question

Here’s some code that throws an exception because of some of the memory management I’m doing:

My Header file:

@property(nonatomic, retain) NSMutableArray *holderArray;

My Implementation file:

@synthesize holderArray

-(void) viewDidLoad{
    holderArray = [[NSMutableArray alloc] init];
    [self addSampleObject];
}

-(void) addSampleObject{
    [holderArray addObject:[self createSampleObject]];
}

-(ModelObject *) createSampleObject{
    ModelObject *mObj = [[ModelObject alloc] init];
    // Set a few properties
    return [mObj autorelease];
}

What should be happening in this context? createSampleObject autoreleases the object at some point, while [holderArray addObject] increments the reference count for that object by 1. From what I understand, it should all be good.

But when a getter accesses that element, I’m getting the following exception. It disappears if I remove the autorelease stmt when creating the model object –

#0  0x012525a8 in objc_exception_throw ()
#1  0x010f36e5 in -[__NSArrayM objectAtIndex:] ()

Am I missing something fundamental about how autorelease works?

Thanks,
Teja.

EDIT: Actually you’re right, there’s a completely unrelated piece of my code that was throwing this error. I thought the only thing that I’ve changed from a working one is adding the autorelease statement.

Thanks!

Answer 1

I think your error might be in the getter – that looks more like an index out of bounds issue than a memory management one.

Your understanding of memory management seems to be correct, the only thing I would note is that the use of the word “create” in a method suggests that the returned object is not autoreleased. Not sure what your actual method names are like, I know this is just sample code.