iPhone memory consumption

Question

I have developed an iphone application that opens to a tabbed view with the first tab being a uinavigationcontroller. Within that controller is a uiviewcontroller that contains a uitableview. There are 2 items listed in the tableview. When I select one or the other item, it displays yet another uiviewcontroller with dynamically generated uiviews.

When I press the "Back" button at the top of the navigation control, to return to the previous uiviewcontroller (that contains the tableview), and then I select 1 of the 2 items in the uitableview again, it eats up almost 2M of memory according to Instruments. This occurs each time, until it reaches about 24M, and my application crashes.

I am registering no leaks whatsoever.

Is there something I need to be doing when the "Back" button is pressed to release the memory allocated to the uiviewcontroller.

Answer 1

The navigation controller retains all view controllers pushed onto its stack, so if you ensure that such view controllers are autoreleased or that you otherwise have no claim on them (e.g., alloc, push, release), they will automatically be released when popped.

If you're doing this and you're still losing memory, perhaps you are over-retaining the your custom views from their view controllers?

It's difficult to say without seeing code, but one thing that might be useful is implementing -didReceiveMemoryWarning on all your UIViewControllers and logging details of them -- then if you see a memory warning from a view controller you think should have been deallocated, you have a starting point for further investigation.

Also, have you tried the Clang Static Analyzer? The Leaks tool is useful, but gives plenty of false negatives. The CSA is no panacea either, but it catches some things Leaks misses.

Answer 2

I'm not sure how far you are in iPhone development, or how much you know about the memory management, but it could be a reference counting issue. Remember: If you call alloc or retain, you need to call release, and never call release on something you haven't alloc'd or retained.