Selecting 'attribute id' not 'object id'

HI --

When a user logs in I want to grab the room he lives in by its id but I
can't seem to get only the room id!

session[:current_room_id] = Person.find(session[:person_id]).rooms.id

returns this for 'session':

--- !ruby/object:CGI::Session
data: &id001
:person_id: 1
:person_name: Test User
:current_room_id: 57306370 <--ARRAY OBJECT ID
:person_role: user
flash: !map:ActionController::Flash::FlashHash {}

But I don't want to the object id of the room array, I want the specific
Room.id so I can call it back with the session when I need it. Taking
out'.id' returns an object array:

session[:current_room_id] = Person.find(session[:person_id]).rooms.id

returns this for 'session':

--- !ruby/object:CGI::Session
data: &id001
:current_room_id:
- !ruby/object:Room
   attributes:
     id: 1 <--THIS IS WHAT I WANT
     <SNIP>
     width: "25"
:person_id: 1
:person_name: Test User
:current_room: 57306370
:person_role: user

Though I'm thrilled that I was able to pull off the
'Person.find(session[:person_id]).rooms' join on my first try, I'm sure
I am missing some small detail to grab the room id. Any ideas?

If the person only has one room:

   class Person < ActiveRecord::Base
     has_one :room

and

   class Room < ActiveRecord::Base
     belongs_to :person

then you should be able to do:

   session[:current_room_id] = Person.find(session[:person_id]).room.id

If the person has multiple rooms, then you have to decide some way to
decide which one you want to save the id of, out of the array of all
of them.

David