How do I create an local autorelease pool to save up memory?

Question

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

Answer 1

See:

http://stackoverflow.com/questions/65427/how-does-the-nsautoreleasepool-autorelease-pool-work

Answer 2

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.