Apple can't write Swift libraries (at least not ones that are publicly exposed) until the ABI stabilizes, so that will not happen until at least Swift 4. Apple can write Swift apps as long as they don't need to support 32-bit Mac, which they haven't needed to do for years.
Apple can't write Swift libraries (at least not ones that are publicly exposed) until the ABI stabilizes, so that will not happen until at least Swift 4. Apple can write Swift apps as long as they don't need to support 32-bit Mac, which they haven't needed to do for years.