Object Alloc Memory Leak?

ledoslover · June 2011

I have several objects that have NSMutableArrays which will contain other objects that contain ... etc.

When I delete the highest object in the hierarchy, I have memory leaks in all of the [NSObject init] method. They all are identical and look like the following:


- (NSObject1 *)init
{
	arrayOfObject2 = [[NSMutableArray alloc] init];
	return self;
}

And their dealloc methods look like:


- (void)dealloc
{
	[super dealloc];
	for (int i = 0; i < [arrayOfObject2 count]; i++)
	{
		[[arrayOfObject2 objectAtIndex:i] release];
	}
	arrayOfObject2 = nil;
	[arrayOfObject2 release];
}

I don't think that the lower class's dealloc methods are being called because I put an NSLog message in one, and it did not appear.

Any thoughts on why this memory leak is happening? Again, it only occurs when I delete the higher objects.

BrianSlick · June 2011

1. You're doing something really wrong if you are releasing the items in an array while they are still in the array.

2:

arrayOfObject2 = nil;

...ok, so arrayOfObject2 is now nil, so what exactly does this do after that:

[arrayOfObject2 release];

3. That init method makes me cry.

ledoslover · June 2011

BrianSlick;341786 said:
1. You're doing something really wrong if you are releasing the items in an array while they are still in the array.

2:
arrayOfObject2 = nil;
...ok, so arrayOfObject2 is now nil, so what exactly does this do after that:
[arrayOfObject2 release];
3. That init method makes me cry.

Instead of simply pointing out my errors, could you explain what I'm doing wrong? I'm sorry for being relatively new at this. I haven't seen much code for creating your own object, so I tried to do it on my own.

BrianSlick · June 2011

No, first you explain why you are doing what you are doing. I know you haven't seen any examples of an init method like that, and I'm reasonably certain that you have seen init methods in other cases (hint: view controllers) that should give you an idea of what needs to happen.

Being new is no excuse. You knew enough to write the code that you have, and you know enough to use instruments. That's a cop out. If you can't explain why you did something, THAT is the first problem that needs to be addressed.

ledoslover · June 2011

I made that init the way I did because when I tried to add objects to that array in the code, it did not work because the array had not be initialized, so I initialized it. That makes sense to me. I'm not sure what else I'm supposed to do there to prevent you from crying.

BrianSlick · June 2011

Then you're not even pretending to look at other init method examples to see what you should do. If you aren't going to do any work, why should I?

ledoslover · June 2011

- (id)init
{
self = [super init];
if (self != nil)
{
arrayOfObject2 = [[NSMutableArray alloc] init];
}
return self;
}

Is this what you're talking about? And do you think this is what's causing the memory leak?

BrianSlick · June 2011

There you go.

Try it. Do you still leak?

Oh, and I should also add:

4. [super dealloc] should be the last thing you do in dealloc, not the first.

ledoslover · June 2011

BrianSlick;341800 said:
There you go.

Try it. Do you still leak?

Oh, and I should also add:

4. [super dealloc] should be the last thing you do in dealloc, not the first.

Yes. Same leaks, unfortunately.

BrianSlick · June 2011

Ok, so we've addressed #3. That still leaves #1 and #2.

ledoslover · June 2011

- (void)dealloc
{
for (int i = 0; i < [arrayOfObject2 count]; i++)
{
[arrayOfObject2 removeObjectAtIndex:i];
}
[arrayOfObject2 release];
[super dealloc];

}

Is that the proper way to do the dealloc?

BrianSlick · June 2011

It's better than your first attempt. You do not need to manually empty out the array.

ledoslover · June 2011

BrianSlick;341806 said:
It's better than your first attempt. You do not need to manually empty out the array.

I'm not sure what you mean exactly by that. But I've found this method. Is that what you're talking about?

- (void)dealloc
{
[arrayOfObject2 removeAllObjects];
[arrayOfObject2 release];
[super dealloc];

}

I'm still getting leaks.

BrianSlick · June 2011

No, what I'm saying is that if the array is going to die at this point, it will automatically take care of removing the items for you. I guess it doesn't hurt anything to clear it out yourself, but it's not necessary.

But otherwise, your init method is now fine, and your dealloc method is now fine. So if you are still leaking, you have issues elsewhere.

Is your dealloc method being called now?

baja_yu · June 2011

You don't need removeAllObjects at all. What exactly is reporting the leak and with what message? Instruments, or is just Xcode giving you a warning? Are you retaining the array anywhere else?

ledoslover · June 2011

BrianSlick;341809 said:
No, what I'm saying is that if the array is going to die at this point, it will automatically take care of removing the items for you. I guess it doesn't hurt anything to clear it out yourself, but it's not necessary.

But otherwise, your init method is now fine, and your dealloc method is now fine. So if you are still leaking, you have issues elsewhere.

Is your dealloc method being called now?

Yes. Now, how do I safely remove all of these objects? What I was doing was starting at the top and working my way down to the lowest object. I deleted all of the objects at the lower level and worked my way back up.

Is this the correct way to do it?

BrianSlick · June 2011

I don't understand the question. You say that the dealloc method is being called, so what do you mean by "safely remove all of these objects"?

ledoslover · June 2011

To Baja, the leaks were coming from Leaks and they were from the class's init methods.

ledoslover · June 2011

Oh, sorry. I meant that it wasn't being called haha. I apologize.

baja_yu · June 2011

When you put an object in an NSArray, the array will retain it, so you should release it (if you allocated it prior) after adding it to the array. When you release an array it will send a release message to all of its objects as well so that will automatically remove them.

ledoslover · June 2011

So if I have a 3 dimensional array, all I have to do is release the first level of the array?

baja_yu · June 2011

There are no multidimensional NSArrays. The closest thing would an an array of arrays. So following logic, the top array would send release to the arrays it holds and they would in turn send release to objects in them. This should be easy to deduce.

ledoslover · June 2011

I have 3 levels of arrays. An object with an array of an object that has an array of an object, etc.

In order to delete the highest object, I just need to say [highestObject release]?

ledoslover · June 2011

- (id)init // init for Object1
{
	self = [super init];
	if (self != nil)
	{
		arrayofObject2 = [[NSMutableArray alloc] init];
	}
	return self;
}

If anybody is still reading this thread, the leak is coming from the array alloc line, and I have no idea why still! :( :(

dany_dev · June 2011

read this...http://www.iphonedevsdk.com/forum/iphone-sdk-development/26587-slicks-definitive-guide-properties.html

BrianSlick · June 2011

Does this:

arrayofObject2 = ...anything...

...appear anywhere else in your class?

As I said before, the issue is no longer in the code you've posted so far. But you haven't posted any more code.

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