Re: Understanding ARC
Re: Understanding ARC
- Subject: Re: Understanding ARC
- From: Jens Alfke <email@hidden>
- Date: Sun, 25 May 2014 09:46:58 -0700
On May 25, 2014, at 2:07 AM, Jamie Ojomoh <email@hidden> wrote:
> So if I use alloc/init then autoreleasepool doesn't work?
No, I meant that the string hasn’t been autoreleased at all yet, so the pool isn’t going to release it when it exits. The pool “works”, it’s just not necessary.
> Or don't I need autoreleasepool at all?
You don’t need it. You only need an autorelease pool if
(a) You’re running a lengthy loop that allocates/autoreleases objects on every iteration; wrapping the body in a pool, keeps those objects from building up
(b) You’re implementing a C callback, i.e. from something like a CF or Unix API.
> Is there any difference in memory releasing / ARC between a class and a
> instance method?
No. Those are totally unrelated concepts.
> And why is it that memory automatically gets released properly when an
> application quits,
It’s part of the job of an operating system to clean up resources left behind by processes.
> but when a class is released any memory that hasn't been
> freed or released properly hangs around forever? Is this not something
> that can be asked here?
Classes don’t get released, objects do. I’m not quite sure what you’re asking. Within a process, individual memory blocks have to be explicitly freed. NSObject does this by keeping track of reference counts and freeing the memory when the ref-count drops to zero. If an object isn’t released enough times, it’ll stay around until the process quits.
Releasing/freeing objects is kind of like cleaning up your room after you’re done using things; you have to remember to put each thing away.
The process quitting is like your house getting bulldozed. Everything that was in it is gone, there’s nothing left until a new house gets built.
Anyway, YOU ARE OVERTHINKING THIS. Stop trying to figure out when things are getting released — that’s ARC’s job. Just write your code.
—Jens
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