Repeats validator that adds model methods

phase1.rb

module Newton
  module Validator
    class RepeatsValidator < ActiveModel::EachValidator
      def initialize(options)
        @attributes = options[:attributes]
        super
        @how_count = options[:how_count]
        @upto = options[:upto]
      end

      def setup(clazz)
        clazz.class_eval @attributes.inject("") {|s, attr| s += <<END}
          def #{attr}_repeats_error?
            @#{attr}_repeats_error
          end
END
      end

      def validate_each(record, attr, value)
        err = false
        if @how_count.call(record, attr, value) >= @upto
          record.errors[attr] << (options[:message] || "repeats too much")
          err = true
        end
        record.instance_variable_set "@#{attr}_repeats_error", err
      end
    end
  end
end

ActiveModel::Validations.__send__(:include, Newton::Validator)