Elm is a language that compiles to JavaScript that is designed to be somewhat accessible to people already using JavaScript...one could call it a flavor of JavaScript that's influenced by languages like Haskell and not get an argument from me.

On the other hand, this project, though interesting, isn't something that the process of learning Swift and Cocoa would really benefit from. If it seems kind of interesting, starting with Elm as a separate project is probably a better way to get context for evaluating using the Elm architecture in Swift.

Elm is a language for writing web applications. There are a lot of good ideas in the framework and it's a fairly big influence on up-and-coming UI frameworks/approaches but it won't help you write Swift/Cocoa apps directly.

[1] http://elm-lang.org/

This is still more or less at a proof of concept stage, so you won't be able to use it to build apps, but it will introduce you to some functional reactive programming concepts