Rails deep nested/non nested form - ruby-on-rails

Question

I'm trying to create a form handling 4 models at once with 2 nested pairs... Got an error: You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.
Is there someone to guide me with this one? For your info I'm using rails 3.0. and I need to handle the 4 models in the same view... Thanks a lot for your help because this one is driving me nuts for days :)
Here is the controller's code:
def new
#pinvoice = Pinvoice.new
#journal = Journal.new
#compte = Compte.find(:all)
if Journal.last.nil?
then
#internal = 'Pinv1'
else
#internal = 'Pinv' + (Journal.last.id + 1).to_s
end
1.times {#pinvoice.pinvlines.build}
4.times {#journal.lignes.build}
respond_to do |format|
format.html # new.html.erb
format.xml { render :xml => #pinvoice }
end
end
The models code:
class Pinvoice < ActiveRecord::Base
has_many :pinvlines, :dependent => :destroy
accepts_nested_attributes_for :pinvlines
end
class Pinvline < ActiveRecord::Base
belongs_to :pinvoice
belongs_to :compte
belongs_to :pinvoice
end
class Ligne < ActiveRecord::Base
belongs_to :journal
belongs_to :compte
attr_accessor :should_destroy
def should_destroy?
should_destroy.to_i == 1
end
end
class Journal < ActiveRecord::Base
has_many :lignes, :dependent => :destroy
accepts_nested_attributes_for :lignes, :reject_if => lambda { |a| a[:montant].to_s == "0"}
attr_accessor :taux
attr_accessor :compte_tva
validates_presence_of :date
validates_presence_of :texte
validates_presence_of :montant_HTVA
validates_presence_of :banque
validates_presence_of :compte
before_update :delete_lignes
def delete_lignes
#lignes.each do |l|
if l.new_record?
l.save
else
l.destroy
end
end
end
end
and the big one the form:
<%= javascript_include_tag 'javascript_pinvlines_fields_new' %>
<%= form_for #pinvoice do |f| %>
<% if #pinvoice.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#pinvoice.errors.count, "error") %> prohibited this pinvoice from being saved:</h2>
<ul>
<% #pinvoice.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<p>
<%= f.label :internal %>
<%= f.text_field :internal, :value => #internal %><br />
<%= f.label :contact %>
<%= f.text_field :contact, :id => 'test' %>
<%= f.label :date_facture %>
<%= f.date_select :date_facture %>
<%= f.label :montant_total %>
<%= f.text_field :montant_total %>
</p>
<h2>Details</h2>
<%= f.fields_for :pinvlines do |builder| %>
<%= render "pinvline_fields", :f => builder %>
<%end%>
<p><%= link_to_add_fields "Ajouter une ligne", f, :pinvlines%></p>
<h2>Jounal</h2>
<%= fields_for #journal do |j| %>
<%= j.label :date %><br />
<%= j.text_field :date, :size => 10 %> <i> au format YYYY-MM-DD </i><br />
<%= j.label :texte %><br />
<%= j.text_field :texte%><br />
<%= j.label :banque %><br />
<%= j.text_field :banque %><br />
<%= j.label :montant_hors_tva %><br />
<%= j.text_field :montant_HTVA%><br />
<%= j.label :tva_id %><br />
<%= j.text_field :tva_id %><br />
<%= j.label :taux %><br />
<%= j.text_field :taux %><br />
<%= j.label :compte_tva %><br />
<%= j.text_field :compte_tva %><br />
<%= j.label :montant_TVA %><br />
<%= j.text_field :montant_TVA%><br />
<%= j.label :montant %><br />
<%= j.text_field :montant %><br />
<%= j.label :compte %><br />
<%= j.text_field :compte %><br />
<%= j.label :internal %><br />
<%= j.text_field :internal, :value => #internal%><br />
<%= j.label :source %><br />
<%= j.text_field :source%>
<br />
<h2>Lignes</h2>
<div class='container'>
<div class="duplicate">
<%= j.fields_for :lignes do |j| %>
<%= j.label :date %>
<%= j.text_field :date, :size=> 8 %>
<%= j.label :compte_id %>
<%= j.text_field :compte_id, :size=> 8 %>
<%= j.label :montant %>
<%= j.text_field :montant, :size=> 8 %>
<%= j.label :debit %>
<%= j.text_field :debit, :size=> 8 %>
<%= j.label :credit %>
<%= j.text_field :credit, :size=> 8 %>
<br />
<% end %>
</div>
</div>
<%end%>
<p><%= f.submit %></p>
<% end %>

Answer 1

At the end I've found a way to handle this with a call back at the model level.