[Beginning Rails 3] Listing 5-37. Current User Model, in app/models/user.rb

user.rb

require 'digest'
class User < ActiveRecord::Base
  attr_accessor :password
  
  validates :email, :uniqueness => true, 
                    :length => { :within => 5..50 }, 
                    :format => { :with => /^[^@][\w.-]+@[\w.-]+[.][a-z]{2,4}$/i }
  validates :password, :confirmation => true,
                       :length => { :within => 4..20 },
                       :presence => true,
                       :if => :password_required?

  has_one :profile
  has_many :articles, :order => 'published_at DESC, title ASC',
                      :dependent => :nullify
  has_many :replies, :through => :articles, :source => :comments

  before_save :encrypt_new_password

  def self.authenticate(email, password)
    user = find_by_email(email)
    return user if user && user.authenticated?(password)
  end

  def authenticated?(password)
    self.hashed_password == encrypt(password)
  end

  protected
    def encrypt_new_password
      return if password.blank?
      self.hashed_password = encrypt(password)
    end

    def password_required?
      hashed_password.blank? || password.present?
    end

    def encrypt(string)
      Digest::SHA1.hexdigest(string)
    end
end