2 levels nested form with a polymorphic association


I'm trying to build a complex nested form for the model 'page', which
has a polymorphic association with different component types.
Unfortunately it does not seem to work properly.

model "Page" :

  has_many :components, :dependent => :destroy
  has_many :textcomponents, :through => :components, :source =>
:componentobject , :source_type => "Textcomponent"
  has_many :componentobjects,:through =>:components
  accepts_nested_attributes_for :components, :allow_destroy => true ,

the polymorphic middle model "Component" :

  belongs_to :componentobject, :polymorphic => true
  belongs_to :page
  accepts_nested_attributes_for :componentobject

a specific component model on the other end 'Textcomponent' :

  has_one :component, :as => :componentobject
  has_one :page, :through => :component

In the 'form' partial of the page controller, I have this code:

<%= form_for(@page) do |f| %>
  <% f.fields_for :components do |cmp_form| %>
  <%= cmp_form.label :cid %>
  <%= cmp_form.text_field :cid %>

  <% cmp_form.fields_for :componentobject do |cmpo_form| %>
    <% if cmpo_form.object.class == Textcomponent %>
      <%= cmpo_form.label :value_nl %>
      <%= cmpo_form.text_field :value_nl %>
    <% end %>
  <% end %>
  <% end %>
<% end %>

And of course in the "Pages" controller I create the nested objects :

  def new
    @page = Page.new
    @c = @page.components.build
    @c.componentobject = Textcomponent.new

    respond_to do |format|
      format.html # new.html.erb
      format.xml { render :xml => @page }

In this case I assume that my 'cmpo_form' part of the form should render
one instance of the the "Textcomponent". Unfortunately it doesn't.... I
like rails is not finding any textcomponents in the component instance
of the page.

I'm not sure if I'm missing something, or it just isn't possible or good

Any suggestions would be welcome.