I was wondering how this would look to clients who were still interested in whether the user was real or not.

Obviously using this pattern should clear up 90% of these cases, but there might still be a few.

As I understand it, it’s impossible in ruby to make a real class look like nil (probably a good thing), so you’d have to do this:

if task.user != user.unassigned_user
# do something special with this assigned task
end

I think that’s OK. It’s a bit more verbose than just calling task.user? but also very clear about what’s going on. I also like the fact that we’ve introduced the first-class concept of an ‘unassigned user’ into the domain.

Wouldn’t it be better to have a record with the Unassigned / Anonymous user? It is a dependence but you can create the record from your application (for example, on startup create_if_not_exists the anonymous user).

The advantage is that you can give AnonymousUser a closer behavior to the normal User. If you have associations with User, you could have to mimic them in Anonymous. Say your User has some roles/memberships/privileges, then it is easier to enforce that your Anonymous has some default role/membership/privilege and to modify/add/delete some in the future.