It only took two months, but I finally finished The Swift Programming Language, Apple’s guide to their new app development language (I linked the web version but actually read the iBooks version so I could highlight and annotate). As far as documentation goes, it’s certainly better than most: informal at times to make it more readable, well thought out examples, really nicely formatted. It seems introductory enough for the beginning programmer (though probably not for someone who has never coded before) but it’s also littered with comparisons to C and Objective-C to provide context for more experienced developers.
A lot of books will be written to teach Swift, but unless you’re totally new to programming, I wouldn’t bother buying one. Apple’s book introduces the language nicely, so I’d save my money for the inevitable slew of texts that’ll cover best practices (once the community establishes best practices) and advanced topics.
In the meantime, make sure you follow Apple’s Swift blog for updates on the language and explorations of features that go a little deeper than their book. If you’re ready for more detailed discussion of the language, I recently found the amazing Airspeed Velocity, which often goes all out in explaining things like nil coalescing . Mattt Thompson has been writing about Cocoa and Objective-C for years at NSHipster and has more recently begun diving into Swift with stuff like this great article on literal convertibles.
There’s a lot of wonderful writing out there already and we’re not even at Swift 1.0 yet. How many great issues on Swift will objc.io put out in the months to come? How cool will it be when Brent Simmons details his journey with Swift on Inessential? I can’t wait for it all.