I have the Swift book open in iBooks, and see the note “For the best experience, open this chapter as a playground in Xcode.” How is this done?
You will see a series of collapsable menus on the left side of the screen detailing different sections, such as “A Swift Tour”, and “Language Guide”. You can click through these to get different bits of information about different aspects of the language.
Many sections will feature the “Open Playground” links that you’ve described, except from here, they’re clickable. When you click one of these "Open Playground" links, the .playground
file associated with this section will be downloaded to your downloads folder, and can be directly opened with Xcode 6.
There is even another option that allows you to open the playground files directly without first dropping them in your downloads folder.
In the documentation viewer in Xcode 6, search for "A Swift Tour", or any other term that you find to yield you an article you're looking for:
Click a result that has a .playground icon to its left. From here, you can use the "Action" button on the right side of the window to open the file directly in an Xcode Playground.