I can register but can not update the object ride. What is the solution for this? (I'm using Ruby 1.9.3, Rails 3.2.8 and MongoID 3.0.0)
<b>the source code</b>
https://github.com/candidosales/querocarona

<b>NoMethodError in RidesController#update</b>
<pre>undefined method `id' for "50b8290e4d7d2c51fa000006":String

app/controllers/rides_controller.rb:40:in `update'
</pre>
<b>Parameters</b>
<pre>{"utf8"=>"✓",
"_method"=>"put",
"authenticity_token"=>"Oc1Ip+sKe8tOEaT9pVMY3jU3KiP4G0gYFwfmRorIBr0=",
"ride"=>

{"driver"=>"50b8290e4d7d2c51fa000006", "requestor"=>"50b8290e4d7d2c51fa000006", "initial"=>"Centro", "destination"=>"JOckey"}

,
"commit"=>"Update Ride",
"id"=>"50b83b624d7d2c0f8000000b"}</pre>
<b>log console</b>
<pre>
Started PUT "/rides/50b8297d4d7d2cd04b000008" for 127.0.0.1 at 2012-11-30 09:24:15 -0300
Processing by RidesController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"Oc1Ip+sKe8tOEaT9pVMY3jU3KiP4G0gYFwfmRorIBr0=", "ride"=>

{"driver"=>"50b8290e4d7d2c51fa000006", "requestor"=>"50b83b544d7d2c230500000a", "initial"=>"Mocambinho", "destination"=>"Centro"}

, "commit"=>"Update Ride", "id"=>"50b8297d4d7d2cd04b000008"}
MOPED: 127.0.0.1:27017 COMMAND database=admin command={:ismaster=>1} (1.1415ms)
MOPED: 127.0.0.1:27017 QUERY database=querocarona_development collection=rides selector=

{"_id"=>"50b8297d4d7d2cd04b000008"}

flags=[:slave_ok] limit=0 skip=0 fields=nil (0.4654ms)
MOPED: 127.0.0.1:27017 QUERY database=querocarona_development collection=users selector={"$query"=>

{"_id"=>"50b8290e4d7d2c51fa000006"}

, "$orderby"=>{:_id=>1}} flags=[:slave_ok] limit=-1 skip=0 fields=nil (0.4120ms)
MOPED: 127.0.0.1:27017 QUERY database=querocarona_development collection=rides selector={"$query"=>

{"requestor_id"=>"50b8290e4d7d2c51fa000006"}

, "$orderby"=>{:_id=>1}} flags=[:slave_ok] limit=-1 skip=0 fields=nil (0.5767ms)
Completed 500 Internal Server Error in 7ms

NoMethodError (undefined method `id' for "50b8290e4d7d2c51fa000006":String):
app/controllers/rides_controller.rb:40:in `update'

Rendered /home/candidosg/.rvm/gems/ruby-1.9.3-p286/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.9ms)
Rendered /home/candidosg/.rvm/gems/ruby-1.9.3-p286/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.7ms)
Rendered /home/candidosg/.rvm/gems/ruby-1.9.3-p286/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (11.1ms)

</pre>
<b>RidesController#update</b><pre>def update
@ride = Ride.find(params[:id])
flash[:notice] = 'Ride was successfully updated.' if @ride.update_attributes(params[:ride])
respond_with @ride
end</pre>

<b>model ride</b>
<pre>
class Ride
include Mongoid::Document
field :initial, type: String
field :destination, type: String
field :created_at, type: Time , default: Time.now

belongs_to :driver, class_name: "User"
belongs_to :requestor, class_name: "User"

end

</pre>

<b>model user</b>
<pre>
class User
include Mongoid::Document
field :name, type: String
field :username, type: String
field :email, type: String

has_one :ride, inverse_of: :driver
has_one :ride, inverse_of: :requestor

end
</pre>