elm-rails makes it easy to use Elm modules in your Ruby on Rails applications. This project was heavily inspired by react-rails.

Only works with Elm 0.19.

This gem is tested against Ruby versions 2.7, 3.0, and 3.1; and Rails versions 6.1, and 7.0. It may work on other versions, and if you want to open a PR adding tests against those versions they would be welcome.

1. Add elm-rails to your Gemfile and run bundle install

   gem "elm-rails"

2. Create a new directory to house all Elm modules

   mkdir app/assets/elm

3. Update .gitignore to ignore elm files

   /elm-stuff
   

1. Define your elm modules in the app/assets/elm directory.

   app/assets/elm/Hello.elm

   module Hello exposing (..)
   
   import Html exposing (text)
   
   port noun : String
   
   main =
     text ("Hello " ++ noun)

2. Open your app/assets/javascripts/application.js and require your Hello.elm.

//= require Hello

3. Use the view helper to insert your component into your view. Pass port values as a Hash.

   <h1>This is an Elm component!</h1>
   <%= elm_embed('Elm.Hello', { noun: 'World!' }) %>

4. That's it!

By default, elm-rails uses elm-compiler under the hood, which will use the version of elm available in your system path, and then installing its own copy in /tmp if needed. If you wish, you may configure this path in an initializer: config/initializers/elm_compiler.rb erb Elm::Compiler.elm_path = "bin/elm"