Kickstarter uses “Swift Playgrounds for iterative development and styling. Most major screens in the app get a corresponding playground where we can see a wide variety of devices, languages and data in real time.” (The Kickstarter iOS app is open-source [0]; see their playgrounds [1].)

Here’s [2] Brandon Williams’ talk Finding Happiness in Functional Programming (starts at “Playground-Driven Development,” but I suggest watching the whole talk), [3] the Swift Talk episode “Playground-Driven Development” (Brandon Williams and Chris Eidhof), and [4] the Swift Talk episode “Test-Driven Reactive Programming” (Lisa Luo and Chris) wherein they build a small but complete PoC all within Playgrounds.

There are many more examples, such as Chris Lattner’s own Dynamic Member Lookup proposal [5] Python Interop playground [6] and Reactive Swift’s getting started playgrounds [7].

Playgrounds are very much entangled with Swift’s core (value proposition).

[0] https://github.com/kickstarter/ios-oss

[1] https://github.com/kickstarter/ios-oss/tree/master/Kickstart...

[2] https://www.youtube.com/watch?v=A0VaIKK2ijM&feature=youtu.be...

[3] https://talk.objc.io/episodes/S01E51-playground-driven-devel...

[4] https://talk.objc.io/episodes/S01E53-test-driven-reactive-pr...

[5] https://github.com/apple/swift-evolution/blob/master/proposa...

[6] https://lists.swift.org/pipermail/swift-evolution/Week-of-Mo... (download the attachment)

[7] https://github.com/ReactiveCocoa/ReactiveSwift/tree/master/R...