How to initialize field based on another field?

Question

I have a user model with :email and :user_name, I want to auto initialize :user_name with part of :email.

class User
  include Mongoid::Document
  field :email
  field :user_name
end

I use simple_form to create the user. How can I initialize :user_name based on :email?

did any of the answers solved your question or do you need further details? — Enrique Fueyo, Oct 14 '13 at 10:46

score 2 · Accepted Answer · answered Oct 08 '13 at 07:08

2

In your model:-

before_create :add_user_name

private
  def add_user_name
    self.user_name = self.email
  end

answered Oct 08 '13 at 07:08

Nikita Singh

score 1 · Answer 2 · answered Oct 08 '13 at 08:27

1

Use default:

class User
 include Mongoid::Document
 field :email, type: String
 field :user_name, default: ->{ "email_is: #{email}" }
end

"If you want to set a default with a dependency on the document's state, self inside a lambda or proc evaluates to the document instance."

Tested with rails c:

u = User.new email: "name@domain.com"
u.user_name # => "email_is: name@domain.com"

answered Oct 08 '13 at 08:27

Enrique Fueyo

No need to use self. self.email or email will do the work. Besides this will work even with users created in the database before the default user_name was implemented. – Enrique Fueyo Oct 15 '13 at 09:32
It throws error if not using `self.email` when create the user in rails console. – AZ. Oct 16 '13 at 02:21
Which rails/mongoid versions are you using. It works for me tested with ruby 1.9.3, rails 3.2.0 and mongoid 3.1.5 – Enrique Fueyo Oct 16 '13 at 14:11

2 Answers2