Custom field names in Rails error messages

The defaults in Rails with ActiveRecord is beautiful when you are just getting started and are created everything for the first time. But once you get into it and your database schema becomes a little more solidified, the things that would have been easy to do by relying on the conventions of Rails require a little bit more work.

In my case, I had a form where there was a database column named “num_guests”, representing the number of guests. When the field fails to pass validation, the error messages is something like

Num guests is not a number

Not quite the text that we want. It would be better if it said

Number of guests is not a number

After doing a little bit of digging, I found the human_attribute_name method. You can override this method in your model class to provide alternative names for fields. To change our error message, I did the following

class Reservation < ActiveRecord::Base
  validates_presence_of :num_guests
      :num_guests    => "Number of guests"
  def self.human_attribute_name(attr)
      HUMAN_ATTRIBUTES[attr.to_sym] || super

Since Rails 2.2, this method is used to support internationalization (i18n). Looking at it, it reminds me of Java’s Resource Bundles and Spring MVC’s error messages. Messages are defined based off a key and there’s a chain of look ups that get applied to resolve an error’s message.

Although, I don’t see myself doing any i18n work in the near-term, it is cool that we have that option now in Rails.

Custom field names in Rails error messages

5 thoughts on “Custom field names in Rails error messages

  1. thirstydog says:

    Turns out that instead of overriding human_attribute_name method you could provide a translation (to English) for activerecord.attributes.reservation.num_guests – it would work the same.

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