Releasing object due to retain count

Question

Hi all,

I have an issue with releasing a view too many times. Although simple in theory because im moving uiview to uiview, which is a subclass of uiview and being animated and so on its not something that I can easily fix. It only crashes 10% and only under certain conditions and only 30% of the time even under these conditions.

So in other words its kinda complex. Sometimes in my dealloc method the retain count of this UIView is already 1 (which gets released when the view is released) and so shouldn't be released again. So what I did is this:

if ([mainView retainCount] > 1) {
    NSLog(@"released");
    [mainView release];
}

Consistant with the crashes released is usually called, but not always and it happens pretty much when I would sometimes expect it to crash. I've checked for leaks with this code and it never leaks.

Now the actual question... Is it wrong to release something due to its retain count? I've tried many different ways to fix this and so far this is the only reliable and non leaking one.

EDIT: If no then what is the better way to copy one UIView to another UIView?

mainView = newView;
[newView release];

I've tried releasing the mainView first then calling copy on the newView but this crashes. The above also works perfectly except the retain count is sometimes 1 lower than expected even though its never released ANYWHERE else in the code.

Answer 1

Do not use the retainCount value.

Seriously, you should never use that value for anything really useful like this.

If you have memory leaks, or experience crash due to overreleases, fix them - they are bugs! And this is not the way to handle them.

Edit: Always a good read: Memory Management Guide

Answer 2

mainView = newView;

it is not a copy but an assignment. The retainCount will be not increase. Then you don't have to make a release.

Answer 3

Do not use -retainCount.

The absolute retain count of an object is meaningless.

You should call release exactly same number of times that you caused the object to be retained. No less (unless you like leaks) and, certainly, no more (unless you like crashes).

See the Memory Management Guidelines for full details.

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In this specific case, releaseing an object when you did not retain it is a recipe for disaster. If it doesn't crash now, it will someday, possibly due to a software update or seemingly unrelated change. It might only be working now because your memory management is wrong everywhere else.

As was stated, this:

mainView = newView;
[newView release];

Is not making a copy of the view. Worse, it is over-releasing the view (because nowhere do you retain it).

Using the copy method on views is not the right solution or, at least, would be exceedingly atypical. UI elements are not copied in that fashion.

Have you tried build and analyze and fixed any errors it indicates?

leaks may not show anything because there may still be a pointer to the leaked object floating about in reachable memory.