Adding CORS support to a Ruby on Rails app working with a Squawkbox editor session

application.rb

require File.expand_path('../boot', __FILE__)

require 'rails/all'

Bundler.require(*Rails.groups)

module MyApp
  class Application < Rails::Application

    # etc., etc.

    config.middleware.insert_after Rails::Rack::Logger, Rack::Cors, logger: Rails.logger do
      allow do
        origins 'localhost:3000', '127.0.0.1:3000', /(app|staging|dev).mysquawkbox.com/
        resource '*', headers: :any, :methods => [:put, :post, :get, :options]
      end
    end
  end
end

Gemfile

source 'https://rubygems.org'
gem 'rails'

# etc, etc.

gem 'rack-cors', require: 'rack/cors'