Apple open source https://swift.org/ https://github.com/apple/swift
Swift Language intro
http://www.raywenderlich.com/115253/swift-2-tutorial-a-quick-start
The Swift Programming Language (Swift 2.1) https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/index.html#//apple_ref/doc/uid/TP40014097-CH3-ID0
the source code https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.playground.zip
swift playground https://www.objc.io/issues/16-swift/rapid-prototyping-in-swift-playgrounds/
run swift code online http://swiftstub.com/
swift for web - in progress https://www.perfect.org/
forked repo - animatd splash screen (launchscreen) https://github.com/vitr/OpenBook
###How do I see which version of Swift I'm using in Xcode?
$ xcrun swift -version
http://stackoverflow.com/questions/30790188/how-do-i-see-which-version-of-swift-im-using-in-xcode