ARC - Automatic Reference Counting - iOS 5 + 4

[TTStu]

Woah, this iOS 5 thing keeps getting more and more hectic.

I think the best way forward for new apps (and reworked apps ahem) is to use ARC.

But what are the main points to consider?

Anyone got any resources or a checklist on making arc-enabled apps that are compatible with iOS4 devices also?

For instance, I understand that the compiler adds iOS4 "glue code" to maintain backwards compatibility, and it is possible to switch off ARC on a per file basis, but what about dealloc methods for example?

I often use dealloc to set a delegate to nil. So I guess that'll still have to be done? What about instance variables? Do they get released here? I guess not... so what happens first... the ARC release or the setting of a delegate to nil... erm, I hope I explained myself correctly...

Surely this is all documented somewhere already?

[TTStu]

Hmmm, found this:

Do I still need to write dealloc methods for my objects?

Maybe.

Because ARC does not automate malloc/free, management of the lifetime of Core Foundation objects, file descriptors, and so on, you still free such resources by writing a dealloc method.

You do not have to (indeed cannot) release instance variables, but you may need to invoke [self setDelegate:nil] on system classes and other code that isn’t compiled using ARC.

dealloc methods in ARC do not require—or allow—a call to [super dealloc]; the chaining to super is handled and enforced by the runtime.

Here:

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Still doesn't exactly enhance my understanding, nor does it instill confidence in me...

"but you may need to invoke [self setDelegate:nil] on system classes and other code that isn’t compiled using ARC."

MAY need to... how the **** do I know?

Grrr