On May 4, 2009, at 1:31 PM, Stephen J. Butler wrote:
On Fri, May 1, 2009 at 11:18 AM, Jesper Storm Bache
<jsba...@adobe.com> wrote:
I have not used NSXMLParser, but as far as I can tell from your
email,
cleanupShowParsing is called in response to a call to the parser
delegate.
In that case, you should not release the parser (because it is
calling your
delegate and is on the stack).
Try using autorelease instead.
That could also be dangerous. What if the parser sets up its own
autorelease pool while walking the XML document? You could have a
situation like this:
- (void) parse {
[self doSomething];
while (notDone) {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[delegate callbackMethod];
[pool drain];
}
[self doSomethingMore];
}
What you're suggesting would put the parser into the inner
autorelease pool!
I still maintain that it's never safe to release/autorelease an object
from inside one of it's delegate calls. If it works at all, you're
implicitly relying on an implementation detail that's subject to
change.
I find this idea somewhat suspect. It seems to undermine the basic
function of the autorelease call, which is delay a release until later.
The reasoning here could be taken to the point of absurdity. This is
because a 'callee' (self, that is) never knows whether the caller has
wrapped the called method in an inner autorelease pool. Thus, the
callee never knows whether its own calls to autorelease will be
subsequently turned into releases by the drained pool immediately upon
returning from the called method. Is the callee never supposed to use
autorelease, to be safe?
From the callee's perspective, a call to autorelease defers the
release until the end of the event loop. If the caller does anything
to shorten the lifetime of objects, that's the callers own fault and
responsibility.
In my opinion, the above code is very questionable. You're just asking
for trouble if you create an autorelease pool yourself and then call
out to the unknown, especially to an object for which you only have a
weak reference and who is probably your owner, the delegate. You are
purposely shortening the lifetime of objects, so you're responsible
for making sure nothing important gets deallocated prematurely.
If you really must use code such as the above, I think you should do
[[self retain] autorelease] before creating the pool.
-Jeff
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