problems returning collection_select info to controller

Hi,

I've been working with rails for a couple of months now and I'm
beginning to understand how things work but this has got me baffled.

I want to return the user.id from a selection of a list of user
names. I followed the example from AWD w/ Rails (page 487) on how to
use collection_select but the controller barfs because it wants a user
and the id is coming back as a string.

Here are the code snippets:

FROM THE RHTML FORM:

<% form_for :master, :url => { :action => :create, :id => @master} do |
form> %>

Owner: <%= @users = User.find(:all, :order => "last_name")
      form.collection_select(:owner, @users, :id, :full_name) %> <br/><br/

IN THE CONTROLLER:

def create
  begin
      @requirement = Requirement.new(params[:requirement]) <<<<FAILS
HERE BECAUSE OWNER RECEIVES a STRING INSTEAD OF A USER OBJECT

IN THE MODELS:
master.rb
          belongs_to :owner, :class_name => 'User', :foreign_key =>
'owner'
user.rb
         has_many :owned_masters, :class_name =>
'Master', :foreign_key => 'owner'

I suspect that my form is not quite right but I have already tried
several different combinations, all with the same result that I gave
here. The selection list in the html is being populated correctly
with the names I want but when I return the id the controller says I'm
returning a string and it wants a user object. How do I reconcile
this?

Thanks for any suggestions,

lac