On 14 May, 2013, at 12:30 PM, Andy Lee <ag...@mac.com> wrote:
> On May 13, 2013, at 11:38 PM, Quincey Morris
> <quinceymor...@rivergatesoftware.com> wrote:
>> On May 13, 2013, at 19:41 , Graham Cox <graham....@bigpond.com> wrote:
>>
>>> When you call -removeFromSuperview, the view is deleted, as there are no
>>> more references to it. The other methods are not called because the object
>>> ceases to exist.
>>
>> I believe your warning is apposite, but is not actually the cause of Tom's
>> problem. After removing the view, his code adds it back again. If the view
>> had already been deallocated, you'd expect a pretty big crash pretty soon
>> (though not necessarily immediately).
>>
>> My guess is that the removed view is still retained by something,
>
> I believe ARC keeps it alive by virtue of self being a strong reference. I
> did a quick test and found that if I do
>
> - (void) mouseDown: (NSEvent*) event
> {
> NSView* superView = [self superview];
> [self removeFromSuperview];
> // [superView addSubview: self];
> }
>
> ...then dealloc does in fact get called. But if I uncomment that one line,
> which references self, dealloc does not get called. This is good news -- I
> would want ARC to work regardless of whether it calls non-ARC code, and vice
> versa.
>
well you have several lines in there which reference self, [ self superview ]
and [ self removeFromSuperview ]. The only difference in the last one is that
self is used as a parameter to a call to another object and that may possibly
be the difference.
And the LLVM documents talk about this, they say that self is not retained
during a method call.
http://clang.llvm.org/docs/AutomaticReferenceCounting.html#self
and discuss exactly this risk.
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