Opal Rails

Rails (3.2+, 4.0) bindings for Opal Ruby engine. (Changelog)

Installation

In your Gemfile

gem 'opal-rails'

or when you build your new Rails app:

rails new <app-name> --javascript=opal

Configuration

Add your configuration in config/application.rb with the following contents:

module MyApp
  class Application < Rails::Application
    # These are the available options with their default value:
    config.opal.method_missing      = true
    config.opal.optimized_operators = true
    config.opal.arity_check         = false
    config.opal.const_missing       = true
  end
end

Gotchas

After changing the version of the opal gem (e.g. via bundle update opal) or any configuration flag you should trash the #{Rails.root}/tmp/cache/assets folder, otherwise you could see a cached source compiled before the change.

Usage

Asset Pipeline

// app/assets/application.js.rb

//= require opal
//= require opal_ujs
//= require turbolinks
//= require_tree .

Opal requires are forwarded to the Asset Pipeline at compile time (similarly to what happens for RubyMotion). You can use either the .rb or .opal extension:

# app/assets/javascripts/greeter.js.rb

puts "G'day world!" # check the console!

# Dom manipulation
require 'opal-jquery'

Element.find('body > header').html = '<h1>Hi there!</h1>'

As a template

You can use it for your views too, it even inherits instance and local variables from actions:

# app/controllers/posts_controller.rb

def create
  @post = Post.create!(params[:post])
  render type: :js, locals: {comments_html: render_to_string(@post.comments)}
end

Each assign is filtered through JSON so it's reduced to basic types:

# app/views/posts/cerate.js.opal

post = Element.find('.post')
post.find('.title').html    = @post[:title]
post.find('.body').html     = @post[:body]
post.find('.comments').html = comments_html

As an Haml filter (optional)

Of course you need to require haml-rails separately since its presence is not assumed

-# app/views/posts/show.html.haml

%article.post
  %h1.title= post.title
  .body= post.body

%a#show-comments Display Comments!

.comments(style="display:none;")
  - post.comments.each do |comment|
    .comment= comment.body

:opal
  Document.ready? do
    Element.find('#show-comments').on :click do |click|
      click.prevent_default
      click.current_target.hide
      Element.find('.comments').effect(:fade_in)
    end
  end

Spec!

Add specs into app/assets/javascripts/spec:

and then a spec folder with you specs!

# app/assets/javascripts/spec/example_spec.js.rb

describe 'a spec' do
  it 'has successful examples' do
    'I run'.should =~ /run/
  end
end

Then visit /opal_spec from your app and reload at will.

License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

stevebooks/opal-rails