This chapter presented playgrounds, an innovative way of running Swift code with graphical representations of values and introspection of running code. Both expressions and the timeline were presented as a way of showing the state of the program at any time, as well as graphically inspecting objects using QuickLook. The XCPlayground framework can also be used to record specific values and allow asynchronous code to be executed.

Being able to mix code and documentation into the same playground is also a great way of showing what functions exist, and how to create self-documenting playgrounds was presented. In addition, tools for the creation of such playgrounds using either AsciiDoc or Markdown (CommonMark) were introduced.

The next chapter will look at how to create an iOS application with Swift.