Rails greater_than model validation against model attribute

Question

I\'ve got a Trip model, which among other attributes has a start_odometer and end_odometer value. In my model, i\'d like to validate that the end odometer is larger than the st

Answer 1

You can validate against a model attribute if you use a Proc.

In rails4 you would do something like this:

class Trip < ActiveRecord::Base
  validates_numericality_of :start_odometer, less_than: ->(trip) { trip.end_odometer }
  validates_numericality_of :end_odometer, greater_than: ->(trip) { trip.start_odometer }
end