I made an Xcode playground to showcase many of the new features coming in Swift 4.2, like I did last year for Swift 4.0. You can download it on GitHub.

The easiest way to run the playground is to install the most recent beta version of Xcode 10 (which ships with Swift 4.2). You can also run it in Xcode 9.4, but that requires installing a recent Swift 4.2 snapshot.