A high-level Swift web framework for OS X and Linux.



Fly: A Swift Web Framework

This is the beginning of some ideas for a Swift web framework intended to be run on linux.

Adapters for the server component are implemented for http4swift and Zewo's Epoch. Epoch only compiles on linux, so it is currently disabled.

What makes Fly special?

  • Application code is decoupled from server implementation. This is also true of other areas in Fly, but at this point in the evolution of Swift web frameworks, this is especially important for the HTTP server layer.
  • The Swift compiler is strongly relied upon for as much as possible. Every use of String in the framework introduces the potential for bugs that cannot be caught by the compiler.
  • Router is built on generics, making it usable in many contexts. The Request and Response objects can be any type, so in the context of an iOS app for deep linking into the app, you might use a String as the Request, and a Bool as the response, simply indicating success or failure.
  • Build HTML views directly in Swift with SwifTML. We'll see if this is a good idea long-term, but I find this preferable to existing Swift templating solutions like mustache.
  • Comes with a fly command line tool that assists in development, similar to rails.


  • Protocol-Oriented. Components of Fly should be connected via protocols so that they can are useful outside of Fly, or can be replaced entirely by other libraries.
  • Concise, but not at the expense of clarity, flexibility, or advantageous use of the type system.
  • Compiler-focused. Fly attempts to lean heavily on the type system to reduce bugs and potential for errors by pushing as much as possible to the compiler. This means:
    • Avoiding throwing out type data by using Any and AnyObject
    • Reducing the use of strings in subscripts for fetching data.

Each use of String in a framework or your application increases the surface areas for bugs that the compiler can't catch.

Component Libraries:





  • Localization
    • Use enum with associated values for localization of strings that require arguments
    • Provide a tool to help devs create localization files based on the added enum cases?
  • A model layer that enables code sharing between server and client apps. This would expose the same API to each type of app, but the implementation that is called would change based on the app configuration. Not sure this is a good idea, but interesting :)

Swift Version