I have been battling a retain cycle for a couple of hours, assuming I am at
fault, but I am starting to think there is something fishy going on. Can
anybody advise?
- I have a window controller subclass (and associated window) A, and a separate
window controller subclass (and associated window) B. B contains a property,
designated 'retain', that keeps a pointer to A. B is programatically closed
first, and later on A is programatically closed
- I believe that I am correctly balancing retain/release for A.
- I believe I am doing the same for B.
1. If I do not set B's pointer to A, both A and B are deallocated correctly
2. If instead I set B's pointer to A, but reset it to nil just before B is
closed, both A and B are deallocated correctly
3. If instead B still has a live pointer to A when B is closed, this should be
autoreleased by the runtime, which it is. However, A never gets deallocated.
There appears to be some weird runtime voodoo behind the scenes involving
NSAutounbinder, which I think is what should ultimately be sending the final
release to A. That is what sends the final release to B, but that final release
for A is missing under that third scenario above.
I am concerned by the following post:
http://theocacao.com/document.page/18
This seems to imply there is some dodginess behind the scenes that Apple have
bodged to try and make things work. The blog post is 8 years old, so I would
have hoped this would be sorted by now(!), but it does sound remarkably close
to my scenario here.
I may have missed out some important relevant information here, so let me know
if I need to be more specific about what I am doing, but can anybody suggest:
- If you agree the problem is likely to be with the runtime rather than with my
code
- What the best workaround would be (scenario 2 above will probably do as a
workaround...)
- Whether the fact that I am hitting this suggests I am doing something out of
the ordinary that I should probably be doing differently.
Thanks for any advice
Jonny
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