why delegates should be unsafe_unretained and not weak?

Question

I added ARC to an app I'm working on. Unfortunately, it crashes. I found that the automatic script which updates all apps to ARC gave __unsafe_unretained qualifier to all id< protocolName> type.

1. Why isn't it a weak type? I have deployed the app and all its sub-projects to iOS 5, and therefore I do have weak qualifiers.

2. My main problem is if I declare those delegates as strong, I'll have a retain-cycle. If I do not, the next time I call them they will be zombies. I checked and before my app crash, the delegate is NSZombie.

What is the cause of this crash and how can it be prevented?

Answer 1

Took some time but i solved it:

1. I deployed the .xcodeproj projects to iOS 5, but the targets were left in iOS 4.3 deployment. When i fixed it (it's in the 'build settings' for each target) - i could change all '__unsafe_unretained' to '__weak', and all 'unsafe_unretained' to 'weak'.

2. To avoid retain cycle those delegates should be weak, and they won't be zombies anymore (because they are weak and not unsafe_unretained), and the app won't crash anymore.

If i was still using iOS4.3-, and there isn't unsafe_unretained qualifer, i should only assign nil to those delegates after i don't need them anymore.