Swift doesn't have a GC from what I know it has automatic reference counting. It's not really the same thing.

It's on compile time and not at run time. It injects release/retain calls between acquiring ownership and relinquishing ownership.

I could be wrong but I don't think they added GC to Swift, as Objective-C (at least not on Mac OS) doesn't have it.

EDIT: They got rid of the GC on Mac OS as well. They use ARC there as well just like iOS.