Re: Memory Management question
Re: Memory Management question
- Subject: Re: Memory Management question
- From: Scott Wilson <email@hidden>
- Date: Thu, 25 Dec 2008 23:49:16 -0800
Okay, but just to be absolutely clear (so I can be sure I'm
understanding this correctly):
1) desiredURL is a local to my method. It is not used outside the
method's scope.
2) I get the exception within my method, not anywhere afterwards. I
didn't think you had to retain objects passed as arguments into a
method unless you wanted to use them beyond that scope. (That would
certainly make things more complicated than I'd thought!)
Am I missing something?
Thanks!
S.
Indeed, you have no way of guaranteeing that link still exists as
you are not explicitly claiming ownership to it. In the first case
of your if, you receive an autoreleased NSURL instance (a new object
created by using the contents of the link object). In the second,
all your code is doing is deciding that desiredURL should point to
the same object as link without claiming ownership of it. To ensure
that you hold ownership of it, you need to explicitly retain it
(code executing in the context of another thread might release it
and cause it to receive -dealloc) or copy it (the former probably
being the more appropriate in this case). Following that, it should
be released when it is no longer of any relevance in this particular
context.
Therefor, I think you'll find that your findings are indeed the
expected behavior - if it's worked in the past it's due more to luck
than to anything else.
-rob.
On Dec 25, 2008, at 2:30 PM, Scott Wilson wrote:
I have an odd case. I've got a NSTextView delegate method which
looks like this:
- (BOOL) textView: (NSTextView *) textView
clickedOnLink: (id) link
atIndex: (unsigned) charIndex
{
...
NSURL *desiredURL;
// is it a NSURL link or a NSString link?
if ([link isKindOfClass: [NSString class]])
{
...
desiredURL = [NSURL URLWithString: [link
stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]
relativeToURL: lastOpened];
} else if ([link isKindOfClass: [NSURL class]]) // this is the case
which causes the problem!!
{
desiredURL = link; // it's a regular file:// URL
} else return NO;
NSLog(@"url %@", [desiredURL path]); // get EXC_BAD_ACCESS if link
was an NSURL
...
}
If I change the code above to desiredURL = [link retain] everything
is fine. I've used very similar code with no problems in a different
context.
Is it possible that link is being autoreleased before my method has
returned?
Thanks
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