Xcode 4.2, 10.7 SDK, target 10.6, ARC ("weak" pointers must be
unsafe_unretained).
I had the following problem, which I solved, but I don't trust the solution:
When I used heapshotting to see what happened when I repeatedly opened and
closed my document, I was accumulating a lot of memory as the document and its
data were never released. All the retains and releases with my code in the
stack trace were balanced.
The document's NIB (no, I don't put the document in the NIB, and I'm using the
window controller that comes with the document) contains an NSObjectController
and an NSArrayController at the top level. Per "Patterns for Managing Outlets
Become Consistent Across Platforms" in the "Transitioning to ARC Release
Notes," the IBOutlet properties for those controllers were declared strong.
But my residual retain count was 2, and a couple of the retains were in the
NIB-loading mechanism, so I tried setting the outlets for those controllers to
nil at -windowWillClose: time.
This cured the leak. So did making the outlets unsafe_unretained (though that
leaked slightly more).
I don't see that there should be _harm_ in this, but I worry, because it goes
against the documentation (at least the documentation I could find). I've
developed a theory, and I'd like to know if it's superstitious:
• For projects targeting 10.7 or later, and using ARC, the references should be
strong, as documented. (But how does the OS know whether that class in
particular is using ARC? Products can be mixed.)
• If the target is 10.6, even if running on 10.7, regardless of whether ARC is
used, the references should be unsafe_unretained/assign, to match the behavior
of the target operating system.
Do I have this right?
— F
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