Question

Which one of these is better practice?

A) retain and release the object myself later

NSMutableArray* array = [[self getArray] retain];
....
[array release];

B) autorelease from the function returning the object

getArray {
   NSMutableArray* returnedArray = [[[NSMutableArray alloc] init] autorelease];
   .....
   return returnedArray;
}

Answer 1

You could read and follow Apples guidelines on memory management and performance.

Personally I think the reasons for choosing one way over the other:

Using Autorelease pros:

• You can’t stuff it up, memory will be freed at some point. That I like to think of as “falling into the pit of success”.

cons:

• Using autorelease a lot may cause you memory problems as lots of objects build up awaiting be released by the autorelease pools.

Using retain/release pros:

• More control when your memory is used/freed.
• On ios apple recommends that you use release instead of autorelease whenever possible to keep the size of the pool small.

cons:

• Like C/C++ malloc/free new/delete you have to be careful to keep them matched up and it is easy to stuff that up, causing memory leaks.
• For member variables you have no choice, retain/release is it.

I think, whichever style you choose comes down to the situation your code is in and choosing the best style based on there pro’s and con’s. I don’t think there is any one answer to this.