Learn Apple's Swift programming language interactively through these playgrounds.
Programmers familiar with C++ and/or Objective-C.
What you'll need
You will need XCode 6.0 GM (or later) or 6.1 Beta 2 (or later) and probably a Mac to run it on.
Purpose & Goal
More than a primer, these playgrounds are intended to get programmers up to speed on Swift as fast as possible so they can begin using Swift productively.
These playgrounds only cover the language. They do not dig into the Swift Standard Library or other APIs.
To increase your understanding, you are encouraged to experiment with them along the way. Play the 'what-if' game. These are live playgrounds which offer near-realtime feedback of edits.
Source of Content
I created these while working my way through the "Language Guide" section of Apple's book, "The Swift Programming Language". I feel the information from that section is represented here fairly completely and very concisely. Many of the samples come directly from the book. Some portions from the book's "Language Reference" section were also included where I felt a bit more information was helpful.
If you don't already have the book, it's free. You should probably get it.
Thanks to Rafał Wójcik for his quick work to update these playgrounds to incorporate the Swift language changes that came with XCode Beta 3.