Re: Methods that return autoreleased objects?

FROM : Mike Ferris
DATE : Thu Jul 03 17:21:11 2008

>>
>> And, as long as we're on the topic... who can name the only other 
>> exceptional case for the "release only if you alloc,new, copy or 
>> retain" rule?  (It's pretty old-school...)

>
>
> How about if you're implementing an initializer for a class cluster 
> that decides, perhaps based on parameters, that it wants to return 
> an instance of a subclass instead of self?
>
>


Ooh, good one.  Not the one I was thinking of, but absolutely.  In 
this case you're basically fulfilling the contract of the +alloc that 
came before.  The caller of -init had a reference on thge object they 
just +alloc'd, so if you're going to replace it (whether with a 
subclass, a uniqued instance, or whatever) you need the replacement to 
be similarly referenced (and you need to release the original "self".)

The one I was thinking of is more of an edge case, a straight-up 
exception to the rule... it is:

   -[NSCoder decodeValuesOfObjCTypes:, ...]

(But not it's singular variant, oddly enough.)

If you decode objects from a coder this way, they come out with a 
reference.  Not a common method and it has no counterpart in the new, 
preferred, keyed NSCoder protocol.

Mike Ferris