This is the validation of a new user with a basic auth system

user.rb

class User < ActiveRecord::Base
  attr_reader :password

  before_validation :ensure_token
  validates :username, uniqueness: true
  validates :username, :session_token, presence: true
  validates :password, presence: true, on: :create
  validates :password_digest, presence: { message: "Password can't be blank"}
  validates :password, length: { minimum: 6, allow_nil: true }
  
  #...
  
end