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Asked: 2026-05-22T03:22:42+00:00

Let’s suppose I create a few objects and I add them to an array.

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Let’s suppose I create a few objects and I add them to an array.

House *myCrib = [House house];
House *johnHome = [House house];
House *lisaHome = [House house];
House *whiteHouse = [House house];

NSArray *houses = [NSArray arrayWithObjects: myCrib, johnHome, lisaHome, whiteHouse, nil];

Normally, all House objects have a retain count of two, but they’re being autoreleased once. After a while, I decide to release myCrib, even if I’m not the owner — I never retained or initialized.

[myCrib release];

The retain count should drop to zero and my object should be deallocated. My question now is: will this illegal action cause my app to work erroneously or even crash, or will NSArray simply delete my object from its list with bad consequences.

I’m looking for a way to maintain a list of objects, but I want the list to maintain itself. When some object disappears, I want the reference to it to disappear from my array gracefully and automatically. I’m thinking of subclassing or wrapping NSArray.

Thank you.

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1 Answer

  1. Editorial Team

    You should not release myCrib if you are not the owner. To do so is a violation of the memory management guidelines and will make your code extremely difficult to maintain. I cannot stress enough that you absolutely should never do this under any sort of circumstance. You’re asking for crashes; the array has declared ownership of the object, and you must not subvert that ownership in any way.

    So the answer here is: your code is absolutely wrong and you should fix it. If you can’t fix it, you should trash it and start over and keep rewriting it until you’ve come up with another way to achieve the same effect without subverting object ownership. I guarantee that it’s possible.

    If what you want is a weak-referencing array, then there are a couple ways you can do this (this was just asked a couple of days ago):

    1. NSPointerArray – weakly references its pointers. When you use garbage collection, they’re autozeroing (ie, the pointers get removed when the object is deallocated). Unfortunately, this is not available on iOS.
    2. CFMutableArrayRef – you can specify a custom retain and release callback, or just not specify one at all. If you leave them out, the array will simply not retain the objects it contains. However, this does not automatically remove the pointer when the object is deallocated.
    3. DDAutozeroingArray – an NSMutableArray subclass I wrote the other day to provide a weakly-referencing and auto-zeroing array that works on both Mac OS and iOS. However, I strongly encourage you to use this only as a last resort; There are probably much better ways of doing what you’re looking for. https://github.com/davedelong/Demos
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