application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  require 'rack/mobile-detect'

  use Rack::MobileDetect

  # set the Rails request.format (MIME type) to :iphone for iPhone/iPod Touch
  # This allows us to serve separate layouts/views for iPhone/iPod
  case request.headers['X_MOBILE_DEVICE']
  when /iPhone|iPod/ then request.format = :iphone
  else
  end

end

# this throws this error when I run Rails Server:
# Routing Error

# undefined local variable or method `request' for ApplicationController:Class