In my Rails (3.0.10) application, I'm using mongoid (2.1.8) and I'm encountering this exception:

undefined method `scoped' for #<Poster:0x007fa7d691c460>

In my application, I can found a Poster by the id or by a composed name like "composed-name+with+345".
When I use the composed name my scope is working well, but when I use the BSON::ObjectId, it fail with the exception.

So, here is my scope where the exception come from:

scope :from_id_or_string, ->(poster_id_or_string) {
  if BSON::ObjectId.legal?(poster_id_or_string)
    Poster.find(poster_id_or_string)
  else
    Poster.for_ticket(Ticket.parse(poster_id_or_string))
  end
}

When I send the string "name+and+number-1234", the if BSON::ObjectId.legal?(poster_id_or_string) line return false then go to the else and use the for_ticket scope etc... and all work fine.

When I send the string "4e4ff0533ea9403ce300007f", the if BSON::ObjectId.legal?(poster_id_or_string) line return true then go to the Poster.find(poster_id_or_string) line and then I got the exception.

If I do, before the Poster.find this:

puts Poster.find(poster_id_or_string).inspect

it show me the Poster I'm looking for.

Other thing I've tried is to use Poster.where(:_id => poster_id_or_string). It was working in some cases but not all.