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Re: Memory Management

Am Mittwoch, 30.07.03 um 10:12 Uhr schrieb Nat!:

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.

As an example:

s = [[NSString alloc] initWithFormat:@"foo"];

this says, the object lives as long as it isn't freed. You must know your code to determine if s is still valid at a certain point in your code or not.

s = [[NSString alloc] initWithFormat:@"foo"];
[s autorelease];

this says, the object lives at least as long as the autorelease pool exists. (Someone may retain it, but that's OK)
The fact that you should have a good idea when your autorelease pool dies make this less obscure, in fact you can avoid thinking about it in many cases.

I would like to see someone prove to me in working code, that adding an object to an autorelease pool does not guarantee that it will live at least until the pool is purged.

Ciao
Nat!
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garbage. Just because something is offensive crap
doesn't necessarily mean it's any good. - Philip Dick
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 >Re: Memory Management (From: Nat! <email@hidden>)



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