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.

Now ships with a patch to sprockets cache key to include processor version that is also in this pull request.

Usage

Asset Pipeline

You can rename app/assets/javascripts/application.js to application.js.rb. Even if not necessary, it is recommended to change Sprockets' //= require statements to Ruby' require methods. Sprockets' //= require statements won't be known by the opal builder and therefore you can end up adding something twice.

Both of the following examples would work:

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

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

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

require 'opal'
require 'opal_ujs'
require 'turbolinks'
require_tree '.'

As you see in the example above, Opal also gives you a Ruby equivalent of //= 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'

Document.ready? do
  Element.find('body > header').html = '<h1>Hi there!</h1>'
end

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/create.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 a 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 /spec-opal:

and then a spec folder with you specs!

# spec-opal/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 or use the command line with rake opal:spec.

CHANGE from versions pre 0.7.1

Specs used to run out of app/assets/javascripts/spec which was problematic because require_tree . would cause opal/sprockets to compile the specs for non spec running. This could result in bad specs that prevent your application Opal code from compiling, and even if it compiles you'll get exceptions about the test framework methods not being defined. To address this, specs have been moved out of the app/assets/javascripts to Rails.root/spec-opal. The name spec-opal was chosen to put it close to the spec directory. We don't want to put specs in spec directory because we don't want the "backend" rspec to run those.

The location of specs is configurable. To restore the old location of app/assets/javascripts/spec add an initializer file like the below.

# config/initializers/opal.rb
Rails.application.config.opal.spec_location = "app/assets/javascripts/spec"

Similarly, you can put the opal specs in another location via a similar initializer call.

Shared templates

As long as the templates are inside the sprockets/opal load path, then you should be able to just require them.

Let's say we have this template app/views/shared/test.haml:

.row
  .col-sm-12
    = @bar

We need to make sure Opal can see and compile that template. So we need to add the path to sprockets:

# config/initializers/opal.rb
Rails.application.config.assets.paths << Rails.root.join('app', 'views', 'shared').to_s

Now, somewhere in application.rb you need to require that template, and you can just run it through Template:

# app/assets/javascripts/application.rb
require 'opal'
require 'opal-haml'
require 'test'

@bar = "hello world"

template = Template['test']
template.render(self)
# =>  '<div class="row"><div class="col-sm-12">hello world</div></div>'

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.

ruralocity/opal-rails