Rails partial form in a form - ruby-on-rails

Question

I have a Rails app with Expenses that belongs_to Vendors.
While the user is adding a new Expense, they might need to add a new Vendor.
I thought I could just add a button and a Vendor partial to the Expense form.
Like this:
<%= simple_form_for #expense, :html => {:class => 'form-horizontal'} do |f| %>
<div class="span5">
<a data-toggle="modal" href="#vendorform">
<p class="pull-right btn btn-primary btn-mini">New Vendor</p></a>
<%= render :partial => "vendors/vendorform" %>
</a>
<%= f.association :vendor, :label_method => :vendor_name, :label => 'Vendor', collection: Vendor.order('vendor_name ASC') %>
The _vendorform.html.erb looks like this:
<div id="vendorform" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="vendorformLabel" aria-hidden="true">
<div class="modal-header">
<a class="close" data-dismiss="modal">×</a>
<h4 id="vendorformLabel">Add Vendor</h4>
</div>
<div class="modal-body">
<%= simple_form_for Vendor.new do |f| %>
(bunch of fields)
</div>
<div class="modal-footer">
<%= f.submit 'Save Vendor', :class => 'btn btn-mini btn-primary' %>
<a class="btn btn-mini" data-dismiss="modal" href="#">Close</a>
<% end %>
</div>
</div>
This partial shows up OK. But, the Vendor record doesn't get created.
The submit of the partial actually somehow triggers the submit for the Expense. The page comes back with all of the required Expense fields red.
I think it's posting to the Expenses controller when the f.submit button in the Vendor partial is pressed !!!
Do I need something in the Expense controller?
Or is there a better way?
Thanks for the help!

Answer 1

Are you sure the vendor partial is in the same folder as the expense form? If not you should have
<%= render :partial => "folder/vendorform" %>

Answer 2

When you have nested attributes, you should use the simple_fields_for method which help manage associations. Then, remove the submit button for the vendor form and add it to the expense form instead. So the vendor form would be -
<div class="modal-body">
<%= simple_form_for Vendor.new do |f| %>
(bunch of fields)
<% end %>
</div>