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Apple says that this is a good idea for saving memory. What would that look like in code?

teedyay
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Thanks
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1 Answers1

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Usualy you don't need to create autorelease pool, because system cares about this. But, sometimes you need to do this. It's usualy in big loops. Code would look like this:

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
int i;    
for (i = 0; i < 1000000; i++) {    
  id object = [someArray objectAtIndex:i];
  // do something with object
  if (i % 1000 == 0) {
    [pool release];
    pool = [[NSAutoreleasePool alloc] init];
  }
}
[pool release];

Autorelease pools are kept as a stack: if you make a new autorelease pool, it gets added to the top of the stack, and every autorelease message puts the receiver into the topmost pool.

iPera
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  • Good description. Calling objectAtIndex: however does not add anything to the autorelease pool, so it's OK to use it in a loop without the autorelease pool. – Chris Lundie Apr 12 '09 at 22:07
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    Keep in mind that Apple recommends using [pool drain] instead of [pool release] as a habit for future compatibility with GC environments. – Marc Charbonneau Apr 13 '09 at 01:15
  • @Marc Charbonneau then wouldn't you get a leak for not calling release on the pool? – Dan Rosenstark Jan 10 '11 at 21:46
  • Nope, in a reference counted environment calling drain is the same as calling release. Check the docs for more information on the differences between GC and non-GC environments. – Marc Charbonneau Jan 24 '11 at 03:12