It's tough. I had a book out in 2014 and it's just been re-released as a second edition in 2016 (Swift Essentials) with fixes for all the changes introduced sin

It's tough. I had a book out in 2014 and it's just been re-released as a second edition in 2016 (Swift Essentials) with fixes for all the changes introduced since the initial release. And you can't run the fix-its on a book :-) One thing that has helped with the new openness of Swift's evolution is that I included several upcoming warnings, such as the demise of the ++ and -- operators and the 'standard' for loop. There will have to be a phase change in the future when Swift moves from a "move fast and break things" to a "stable evolution". It has been suggested that this will begin with Swift 3 (when a stable ABI is introduced) but I suspect it will be Swift 4 or 5 when stability is really nailed down.