Rails - Feb 2006 - second table column data lift

have placements, clients and case_managers tables with relationships

Trying to create new placement record...case_manager_id field exists in
clients table. I need the value from related clients record in
placements table

in placements_controller.rb

def create
  @placement = Placment.new(params[:placement])
  case_manager_id = Client.case_manager_id  # this doesn''t work
  if @placement.save
    flash[:notice] = ''Placement was successfully created''
    redirect_to :action => ''list''
  else
    render :action => ''new''
  end
end

How do I get the case_manager_id value from the related record since I
am already storing the client_id (the foreign key) because I need the
foreign key for case_manager_id or I cannot save?

Craig