byte_size_validator.rb

class ByteSizeValidator < ActiveModel::Validations::LengthValidator
  def validate_each(record, attribute, value)
    value_length = value.respond_to?(:bytesize) ? value.bytesize : value.to_s.bytesize

    CHECKS.each do |key, validity_check|
      next unless check_value = options[key]
      next if value_length.send(validity_check, check_value)

      errors_options = options.except(*RESERVED_OPTIONS)
      errors_options[:count] = check_value

      default_message = options[MESSAGES[key]]
      errors_options[:message] ||= default_message if default_message

      record.errors.add(attribute, MESSAGES[key], errors_options)
    end
  end
end