Ruby on Rails - I18n implementation

application_controller.rb

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  include Devise::Redirects
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception
  include Locale
end

locale.rb

# app/controllers/concerns/locale.rb
module Locale
  extend ActiveSupport::Concern

  included { before_action :set_locale, :set_content_language }

  private
    def set_locale
      I18n.locale = session[:locale] = params[:locale] || session[:locale] || I18n.default_locale
    end

    def set_content_language
      response.headers["Content-Language"] = I18n.locale.to_s
    end
end