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)
# install devise first
# gem install devise
# rails g devise:install
# rails g devise User
gem install devise-guests
rails g devise_guests User# 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: nil, email: guest_RANDOMENOUGHSTRING_@example.com, guest: true>