You can use Slim (or Haml) to serve your Batman.js templates in the Rails Asset Pipeline.

1. Include Slim in your gemfile

Add this line to your Gemfile:

```ruby Gemfile gem “slim”

# 2. Register the Slim engine with Rails

Make a new initializer (eg, `config/initializers/slim_assets.rb`) and put this in it:

```ruby config/initializers/slim_assets.rb
Rails.application.assets.register_engine('.slim', Slim::Template)

Credit: Dillon Buchanan

Update: Serving compiled Slim (or Haml) assets in production

When you deploy to production, if you have config.initialize_on_precompile = false, an initializer isn’t going to work. You’ll have to register the Sprockets engine another way. Add it to the application config in config/application.rb:

```ruby config/application.rb module MyApp class Application < Rails::Application # … config stuff … config.before_initialize do |app| require ‘sprockets’ require ‘slim’ # require ‘tilt’ # for Haml Sprockets::Engines #force autoloading Sprockets.register_engine ‘.slim’, Slim::Template # Sprockets.register_engine ‘.haml’, Tilt::HamlTemplate # for Haml end # … more config stuff … end end

Now, you'll have the Slim template engine available even if your app doesn't intialize, which is most notably the case for `bundle exec rake assets:precompile`. Nice!

# 3. Beef up your BatmanController

At time of writing, the `batman-rails`-generated BatmanController won't work right in production. There's an [outstanding PR](https://github.com/batmanjs/batman-rails/pull/46) with a fix. If that's closed, then we're good to go. In the mean time, Make your `app/controllers/batman_controller.rb` look like this:

```ruby app/controllers/batman_controller.rb
class BatmanController < ApplicationController
  def index
    if request.xhr?
      prefix_length = Rails.application.config.assets.prefix.length + 1
      path = request.path[prefix_length..-1]
      render :text => Rails.application.assets[path]
    else
      render nothing: true, layout: 'batman'
    end
  end
end

When this is done, any files ending in .html.slim in assets will be served as rendered HTML in response to XHR (Ajax) requests. Note that all non-XHR requests will still receive the batman layout (but then Batman will respond to the request, so you’re all good).