Error

Started GET "/api/cartypes?location=PHX4" for 127.0.0.1 at 2012-02-28 17:48:25 -0500
Processing by ApiController#cartypes as HTML
  Parameters: {"location"=>"PHX4"}
   (0.6ms)  SELECT car_types.name FROM "car_types" WHERE (locations.code = 'PHX4')
PG::Error: ERROR:  missing FROM-clause entry for table "locations"
LINE 1: SELECT car_types.name FROM "car_types"  WHERE (locations.cod...
                                                       ^
: SELECT car_types.name FROM "car_types"  WHERE (locations.code = 'PHX4')
Completed 500 Internal Server Error in 14ms

ActiveRecord::StatementInvalid (PG::Error: ERROR:  missing FROM-clause entry for table "locations"
LINE 1: SELECT car_types.name FROM "car_types"  WHERE (locations.cod...
                                                       ^
: SELECT car_types.name FROM "car_types"  WHERE (locations.code = 'PHX4')):
  app/models/car_type.rb:10:in `supported_by'
  app/controllers/api_controller.rb:8:in `cartypes'

model

  def self.supported_by(location)
    if location
      includes(:locations).where("locations.code = ?", location.upcase).pluck("car_types.name")
    else
      []
    end
  end