json_on_rack.rb

class JsonOnRack
  def call(env)
    if m = env['PATH_INFO'].match(/load_cities\/(\d)+/)
      cities = City.select([:id, :name]).where(:state_id => m[1]).as_json
      [
        200,
        {"Content-Type" => 'text/plain'},
        [cities]
      ]
    elsif m = env['PATH_INFO'].match(/load_zip_codes\/\d+/)
      [
        200,
        {"Content-Type" => 'text/plain'},
        ['Ok']
      ]
    end
  end
end