devise_strategies_rememberable.rb

require 'devise/strategies/rememberable'

module Devise
  module Strategies
    class Rememberable < Authenticatable
    private
      def remember_key
        key = "_app_remember_#{scope}_token"
        key += "_#{Rails.env.to_s}" unless Rails.env.production?
        key
      end

      def remember_cookie
        @remember_cookie ||= cookies.signed[remember_key] # backwards compatibility
        @remember_cookie ||= cookies.signed["remember_#{scope}_token"]
      end
    end
  end
end

module Devise
  module Controllers
    module Rememberable

      # Remembers the given resource by setting up a cookie
      def remember_me(resource)
        scope = Devise::Mapping.find_scope!(resource)
        resource.remember_me!(resource.extend_remember_period)
        cookies.signed[remember_key(scope)] = remember_cookie_values(resource)
      end

      # Forgets the given resource by deleting a cookie
      def forget_me(resource)
        scope = Devise::Mapping.find_scope!(resource)
        resource.forget_me!
        cookies.delete(remember_key(scope), forget_cookie_values(resource))
        cookies.delete("remember_#{scope}_token", forget_cookie_values(resource))
      end

      private

        def remember_key(scope)
          key = "_app_remember_#{scope}_token"
          key += "_#{Rails.env.to_s}" unless Rails.env.production?
          key
        end

    end
  end
end