app/validators/trailing_whitespace_validator.rb

   1 class TrailingWhitespaceValidator < ActiveModel::EachValidator
   2   def validate_each(record, attribute, value)
   3     if value =~ /\s\z/
   4       record.errors[attribute] << (options[:message] || I18n.t("validations.trailing whitespace"))
   5     end
   6   end
   7 end