mongoid find VS where

i seem to only be having this issue with 1 particular model when i am searching by ID

>> Cart.where(:_id => '4dae5902e1607c232c000009').first
=> #<Cart _id: 4dae5902e1607c232c000009, _id: BSON::ObjectId('4dae5902e1607c232c000009'), _type: nil>
>> Cart.find('4dae5902e1607c232c000009')
Mongoid::Errors::DocumentNotFound: Document not found for class Cart with id(s) 4dae5902e1607c232c000009.

the strange thing is that with other models, i can use find just fine. any ideas?

the rest of the stack is...

from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criterion/inclusion.rb:192:in `execute_or_raise'
from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criterion/inclusion.rb:190:in `tap'
from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criterion/inclusion.rb:190:in `execute_or_raise'
from /Library/Ruby开发者_如何学Go/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criterion/inclusion.rb:106:in `find'
from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/finders.rb:67:in `find'
from (irb):37

Normally the issue is the other way around. With the where failing and the find working.

That is cause by where not casting the id into BSON::ObjectId before the query.

Usually you would have to do this

Cart.where(:_id => BSON::ObjectId('4dae5902e1607c232c000009')).first

This leads me to believe that your ids are stored as strings and not BSON:ObjectId and would explain why find fails ( it is searching for a BSON::ObjectId not a string)

Could also explain why it is only one model as it depends entirely on how the objects are stored.

Hope that helps