Question

I’m re-reading the first few chapters of Cocoa Programming for Mac OS X and the author states that one of NSCalendarDate‘s class method returns an autoreleased object. I always assumed that all class methods returned an autoreleased object (since there’s no alloc involved).

Are there any class methods which you have to specifically retain?

Thanks.

Answer 1

Class methods, just like instance methods, should adhere to the standard Cocoa memory management rules.

You take ownership of an object if you
create it using a method whose name
begins with “alloc” or “new” or
contains “copy” (for example, alloc,
newObject, or mutableCopy), or if you
send it a retain message. You are
responsible for relinquishing
ownership of objects you own using
release or autorelease. Any other time
you receive an object, you must not
release it.

Presumably they are returning an autoreleased object, or a reference to a singleton or something like that. Either way, you need not release the object unless it started with “alloc” or “new” or contained “copy”. You need not retain it unless you’re looking to keep it around past the scope of the current autorelease pool, by storing it in an iVar or something like that.