The playgrounds you’ve seen in the other chapters of this book are one page long (page means a playground page and not necessarily a printed page). The heart of each playground page is the code that assigns the live view of the current page to a view or view controller that contains the playground page:
PlaygroundPage.current.liveView = your playground view
Remember that technically the current page can be any object that conforms to the PlaygroundLiveViewable protocol. Objects that conform to this protocol include UIView, UIViewController, NSView, and NSViewController. Subclasses ...