Question

I’d like to generate unique, anonymous usernames when creating an instance of my User model. Ideally, it would be set by default if I don’t specify any username.

So for example when I do User.create!() I’d like to have the username column set to ‘anonymous123’, where 123 is a unique number taken from a sequence (the value of the id column for that instance would be ok).

Answer 1

Combining the examples from a couple of the answers would do it

class User < ActiveRecord::Base
  before_create :set_anonymous_username

  def set_anonymous_username
    username = "anonymous#{User.last.id + 1}" if username.nil?
  end
end

I have used before_create here because I would expect you only to have to set an anonymous username before you create the User for the first time. The before_save will be called every time the model is saved and could be unnecessary overhead, but either will work