Ruby on Rails: Custom Validator

active_validator.rb

class ActiveValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    # If the relationship exists and the related object is active
    unless eval("record.#{attribute.to_s.gsub("_id", "")}") && eval("record.#{attribute.to_s.gsub("_id", "")}").active
      record.errors.add(attribute, "must be an active #{attribute.to_s.gsub("_id", "")}") unless eval("record.#{attribute}.blank?")
    end
  end
end