# Current user contains the user that is logged in
>> current_user = User.find(6)
>> pp current_user
#<User id: 6, created_at: "2007-12-13 15:30:28", updated_at: "2007-12-13 15:30:33", email: "admin2", password: "dd3ca720302ead1415c21356d3aa2b309a4eaf9b", password_salt: "jU4rX0m9pn", password_hash_type: "sha1">
>> User.find(6).destroy
#<User id: 6, created_at: "2007-12-13 15:30:28", updated_at: "2007-12-13 15:30:33", email: "admin2", password: "dd3ca720302ead1415c21356d3aa2b309a4eaf9b", password_salt: "jU4rX0m9pn", password_hash_type: "sha1">
>> pp current_user.valid?
true
>> User.find(6)
ActiveRecord::RecordNotFound Exception: Couldn't find User with ID=6


# Answer
# In the application controller, first thing, I do is run this code.  It checks to see if the user they had in their session is still valid or not.
begin
  unless User.exists?(current_user)
    raise
  end
rescue
  self.current_user = AnonymousUser.new
end