gistfile1.rb

class User < ActiveRecord::Base
  attr_accessible :email, :first_name, :last_name
  has_one :shopping_cart
  has_and_belongs_to_many :addresses
  has_and_belongs_to_many :payment_options

  validates :email, uniqueness: true, presence: true, format: { with: /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i }
  has_secure_password

  def self.authenticate(email, password)
    find_by_email(email).try(:authenticate, password)
  end

  def self.new_guest
    user = User.new
    user.guest = true
    user.save validate: false
    user
  end

  def name
    if guest
      "Guest"
    else
      "#{first_name} #{last_name}"
    end
  end
end

class ShoppingCart < ActiveRecord::Base
  belongs_to :user
  has_many :items, class_name: 'ShoppingCartItem'
end