Devise Guests

A drop-in guest user implementation for devise

(I'm using "user" to mean my devise model, but you should be able to use any model you want, just like devise)

Installation

# install devise first
# gem install devise
# rails g devise:install
# rails g devise User

gem install devise-guests
rails g devise_guests User

Usage

# Where you might use current_user; now you can use

current_or_guest_user

# which returns

current_user # (for logged in users)

=> User<id: 1, email: ...>
# or 

guest_user # ( for anonymous users)

=> User<id: 2, email: guest_RANDOMENOUGHSTRING_@example.com, guest: true>

Transferring Guest to User on Login

During the login process you may want to transfer things from your guest user to the account they logged into. To do so, add the following method to your ApplicationController:

private
def transfer_guest_to_user
  # At this point you have access to:
  #   * current_user - the user they've just logged in as
  #   * guest_user - the guest user they were previously identified by
  # 
  # After this block runs, the guest_user will be destroyed!
  
  if current_user.cart
    guest_user.cart.line_items.update_all(cart_id: current_user.cart.id)
  else
    guest_user.cart.update!(user: current_user)
  end

  # In this example we've moved `LineItem` records from the guest
  # user's cart to the logged-in user's cart.
  #
  # To prevent these being deleted when the guest user & cart are
  # destroyed, we need to reload the guest record:
  guest_user.reload
end

Custom attribute

If you have added additional authentication_keys, or have other attributes on your Devise model that you need to set when creating a guest user, you can do so by overriding the set_guest_user_params method in your ApplicationController:

private
def guest_user_params
  { site_id: current_site.id }
end

Non-standard authentication keys

By default Devise will use :email as the authentication key for your model. If for some reason you have modified your Devise config to use an alternative attribute (such as :phone_number) you will need to provide a method to generate the value of this attribute for any guest users which are created.

Sticking with the :phone_number example, you should define the following method in your application_controller.rb:

private
def guest_phone_number_authentication_key(key)
  key &&= nil unless key.to_s.match(/^guest/)
  key ||= "guest_447" + 9.times.map { SecureRandom.rand(0..9) }.join
end

Validations are skipped when creating guest users, but if you need to rely on future modifications to the guest record passing validations, then you should ensure that this default value for guests is generated in such a way as to be valid.

Prevent deletion of guest records

By default, when signing in from a guest account to an authenticated account, the guest user is destroyed. You have an opportunity through the logging_in_user callback (or logging_in_MODEL if you're not using User) to transfer data from the guest to the main account before destruction occurs.

However, for some situations such as guest-checkout, you may desire that any guest account which makes a purchase does not get destroyed. In that case you can use the skip_destroy_guest_user method to identify when to skip deleting these records. By default this method returns false, indicating that every record is acceptable for destruction, but you could use something like the following to optionally prevent it:

def skip_destroy_guest_user
  guest_user.orders.any?
end