has_one belongs_to update woes

Hi,

I'm using 2 models, Machine which has_one MachineDetail (which
belongs_to Machine). Machine is a table of computers, MachineDetail
has a foreign key machine_id, and is used to add some additional
information about the computers. They're separate because we're
maintaining a large number of tables, which independently refer to the
machine table, adding additional information for different web
applications.

Everything I've done in Rails so far has just worked, but now that I'm
connecting these two tables together it seems the wheels are falling
off a bit.

I'm looking around for a really simple way of updating both these
tables at the same time. When you edit a computer, you can also edit
parts of the machine_detail table.

The select is fine. I use

@machine = Machine.find(id)

and then can print @machine.details.appearance to get the joined
information. This seems really nice.

With the edit form I'm running into difficulties.

The edit form has

<% form_for :machine, @machine do |f| %>
   <%# ... normal machine properties ... %>

   <%# fields I want to update in the joined table: %>
   <% fields_for @machine.details do |details| %>
      <%= details.hidden_field :appearance %>
   <% end %>
<% end %>

It send POST parameters to the server that look like:

params[:machine][:serialNo]

and:

params[:machine_detail][:appearance]

for the join table.

In my controller, I'm currently doing:

        @machine = Machine.find(params[:machine][:id], :include =>
'details')
        @machine.details = MachineDetail.find(:first, :conditions =>
["machine_id = ?", @machine.id])
        @machine.update_attributes(params[:machine])
        @machine.details.update_attributes(params[:machine_detail])

Is this correct? I'd think you could do an update all in one action.
It's causing my controller to look bloated and confusing.

Thanks,

Luke