Re: Newbie Memory Questions on a Code Fragment
Re: Newbie Memory Questions on a Code Fragment
- Subject: Re: Newbie Memory Questions on a Code Fragment
- From: mmalc Crawford <email@hidden>
- Date: Wed, 21 Jan 2009 10:14:33 -0800
On Jan 21, 2009, at 9:27 AM, Kenneth Bruno II wrote:
On Jan 21, 2009, at 12:04 PM, mmalc Crawford wrote:
When I no longer need it I'll just call release on the object,
this would most likely be done in the dealloc method of the class
in which I initialized my object.
As a general statement, this is at best misleading.
If you maintain an object as an instance variable, you're expected
to provide accessor methods to retain and release it as well.
Not necessarily, the object could be purely for internal use in the
class in which case you wouldn't provide accessor methods.
On the contrary, even if the object is purely for internal use, you
should typically provide accessor methods.
You might not make them public, but using accessor methods pervasively
is the best first step to getting memory management right (especially
for a beginner...).
You should only call release on objects that you have created
through methods that begin with alloc, new, or copy or objects
that you have previously called retain upon. I suggest that you
review the Cocoa Memory Management Rules to understand this further:
<http://developer.apple.com/documentation/Cocoa/Conceptual/MemoryMgmt/Tasks/MemoryManagementRules.html
>
If you review that, you will find that your summary contains a
small but important omission. This is why it's typically better
simply to point to the Guide than to try to summarise yourself.
Which is exactly why I linked to it and suggested that he read it
instead of just relying on my summary.
So why post an inaccurate summary in the first place?
Please, as I've said before, I'm increasingly convinced that most
newcomers' confusion with memory management stems from inaccurate and
misleading advice from forums and the web, so just point to the
documentation.
One small error here, I should have added this line after these
two in order to properly release the NSDateFormatter:
[aFormatter release];
This needs to be done because I created a new NSDateFormatter
which has a retain count of 1.
"Which you don't own..."
Chasing retain counts is one of the surest ways of quickly becoming
confused when trying to track down memory management problems.
I wouldn't ever advocate chasing retain counts, I was simply
pointing out the fact that the object will stay around because I
retained it. I probably should have said "has been retained by me
and must be released" or something similar.
Yes.
mmalc
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