Rails 5 API and CORS

So if you have your frontend and backend on different domains you'll need to allow CORS (cross-origin HTTP request).

Rails 5 with --api mode will prepare the setup for you. You just need to uncomment the following:

# Gemfile
gem 'rack-cors'

# config/initializers/cors.rb
Rails.application.config.middleware.insert_before 0, Rack::Cors do
  allow do
    origins 'localhost:4200'
    resource '*',
      headers: :any,
      methods: %i(get post put patch delete options head)
  end
end