Work with values that haven't been determined yet.

What's New

v4.1.0: Weird Amorphous Blob of Chicken


Deferred 4.1 improves compatibility with Apple's 2019 tools and releases.

This release is compatible with Swift 4.2, 5.0, and 5.1 on Apple platforms and Linux.

  • Bumps Swift version to 4.1, removing remaining use of unofficial Swift annotations for binary resilience.
  • Improves compatibility with Swift Package Manager in Xcode 11.


Deferred lets you work with values that haven't been determined yet, like an array that's coming later (one day!) from a web service call. It was originally inspired by OCaml's Deferred library.

Deferred is a "futures library", probably like ones you've already heard about. Where Deferred aims to be different is by providing a small, efficient API that's easily adopted in our many consulting projects.

Vital Statistics
Requires Swift 4.2 or greater
Under MIT License
Circle CI
Swift Package Manager

Don't Panic!

See Deferred's comprehensive programming guide and documentation at the Deferred Reference.

If you have a question not answered by the guide or the module comments, please open an issue!

Need Some Help?

Deferred, as an open source project, is free to use and always will be. Big Nerd Ranch offers help for Deferred, Code Audits, and general mobile app design/development services. Email us at to get in touch with us for more details.


  • Swift Tools 4.2.0
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Last updated: Sun Mar 12 2023 16:37:24 GMT-0500 (GMT-05:00)