Re: Memory Management
Re: Memory Management
- Subject: Re: Memory Management
- From: email@hidden
- Date: Wed, 30 Jul 2003 22:10:24 -0400
On Wednesday, July 30, 2003, at 09:25 PM,
email@hidden wrote:
Am Mittwoch, 30.07.03 um 01:13 Uhr schrieb John Randolph:
On Tuesday, July 29, 2003, at 11:23 AM, Nat! wrote:
Autorelease pools have some clear semantics. Every object added to
an autorelease pool gains a property, a guaranteed minimum lifetime.
Umm, no.
An object added to an autorelease pool is going to get a -release
message whenever the pool gets released, and that's all. The act of
adding it to the pool has no effect of guaranteeing a minimum >
lifetime.
-jcr
ok, I should have explicitily stated the assumption that the object is
added retained.
But with my answer I am obscuring my own point, that adding it retained
to the pool does guarantee a minimum lifetime. As John states "An
object added to an autorelease pool is going to get a -release message
whenever the pool gets released". That's exactly the minimum lifetime.
It can be longer, but it can't be less.
And adding it non-retained and not crashing is a trick you must show me
as
s = [[NSString alloc] initWithFormat:@"My retain count is 1"]
[s autorelease]; // yes its retained
[s release]; // bad idea
In this example ownership is transferred to the autorelease pool. s can
not die earlier than the enclosing autorelease pool.
"Ownership" is not "transferred" to the autorelease pool, the program
simply
crashes later at the end of the event loop when the autorelease pool is
released
and it sends its release on the "autoreleased" object which no longer
has a retain
count and has already been deallocated.
Always balance your alloc/copy/retain with releases if you have no
further need
for the object or a final autorelease to bring the count to zero if you
return the
object. This way (in general) it's "minimum lifetime" will be to the
end of the
current event loop - when Cocoa releases and recreates the default
autorelease pool.
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