This gem provides support to prevent a request from hitting the controller when the CORS validation fails.

This gem will only work for gem Rack::Cors at version '0.3.0'. At this time, November 18th 2014, the '0.3.0' version is in the 'master' branch, so you need to include the gem like this

gem 'rack-cors', :require => 'rack/cors', github: "cyu/rack-cors", branch: 'master'

In your Gemfile add the line

  gem 'rack-cors-halt'

and then run

bundle

or install it yourself with

gem install rack-cors-halt

In the config.rufile you need to configure the Rack::Cors::Halt middleware by passing it in the use command:

use Rack::Cors::Halt

In your config/application.rb you'll need something like this:

module YourApp
  class Application < Rails::Application

    # ...

    config.middleware.insert_before 1, "Rack::Cors::Halt"
      
  end
end

why .insert_before 1? Typically the first middleware will be the Rack::Cors one, so the best approach is to place the Rack::Cors::Halt beneath that one so no more middlewares are runned.