Dear Erica: Playground Support Folder

“N” asks: “Hey, is the “shared playground folder” long gone, or does it still exist?”

Still there, still useful.

The big difference for long-time playground users is that it moved into the PlaygroundSupport module from the XCPlayground module. The latter was deprecated in Xcode 7. It’s a tiny module that supports playground-specific features. This constant (playgroundSharedDataDirectory) gives you a well-defined sandboxed folder that’s shared between all playgrounds.

This is, by the way, a terrible symbol name (take note!), as it returns a URL. It used to return a string but the name never got updated:

public let playgroundSharedDataDirectory: URL

I often build playground-specific subfolders so my directory doesn’t get all messy.

Another valuable feature is indefinite execution support (needsIndefiniteExecution) for playground pages that have to perform asynchronous work before completion. You can use this support to build little playground-based utilities instead of writing shell scripts.

I have some pages that work with Imgur, Google search, Wolfram queries, etc. A nice thing about building in playgrounds vs shell is that you can integrate audio and visual elements rather than having to save them to files and open them in helper applications.

If you’re writing API utilities, enable manual execution. Constant reloads can almost immediately deplete, for example, your Gist API query count for the day. Oops.

In Xcode, the shared data folder is available for iOS, macOS, and tvOS playgrounds. The shared data folder is not available on iOS’s Swift Playgrounds. This policy discourages custom local storage and access beyond standard media library locations.

There are some further protocols and types under the PlaygroundSupport umbrella in Swift Playgrounds. These aren’t available for Xcode playgrounds because they’re meant for use in Playground Books.

The extra functionality is part of Playground Book support, which underlies the tech in “Learn to Code”, etc. These additional APIs include items like a key-value data store, message passing between the live view and the primary playground page, and more.

If you want to learn more about Playgrounds, I have a book.  It discusses the features you use in Xcode and an overview of how to use iOS Playgrounds. I quite deliberately did not include much about Playground Book authoring as the topics are somewhat orthogonal.

I’ll probably be revising both Playground Secrets and Power Tips and my Swift Documentation Markup after WWDC. There’s also a three-book bundle available with Swift from Two to Three.

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