custom-validator

class AtLeastOneOfValidator < ActiveModel::Validator
  def validate(record)
    fields = Array(options[:fields])
    raise ArgumentError, "provide :fields" if fields.empty?

    return if fields.any? { |field| filled?(record.public_send(field)) }

class Coupon < ApplicationRecord
  before_validation :normalize_code

  validates :code,
            coupon_code: { min_length: 6 },
            uniqueness: { case_sensitive: false }