Multiple fields_for behavior

Rails
1

With the following code and result below, why does the cars_attributes
index (i.e. name=owner[cars_attributes][>>>0<<<][color]) increment in
the second fields_for block when only one car is built? Shouldn’t it
stay the same because only one car was built?

Is this standard behavior? If so, what is the standard way to force
both indexes to be 0 (or increment together if there are more
records)?

This is an over-simplified example. The reason I want two fields_for
blocks is due the arrangement of partials in another complex form.

Much thanks!

Matt

owners_controller.rb

…

def new
@owner = Owner.new
@owner.cars.build

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

end

…

owner.rb

class Owner < ActiveRecord::Base
has_many :cars
accepts_nested_attributes_for :cars
end

car.rb

class Car < ActiveRecord::Base
belongs_to :owner
end

new.html.erb

<%= form_for(@owner) do |f| %>
<% if @owner.errors.any? %>


<%= pluralize(@owner.errors.count, “error”) %> prohibited
this owner from being saved:

  <ul>
  <% @owner.errors.full_messages.each do |msg| %>
    <li><%= msg %></li>
  <% end %>
  </ul>
</div>

<% end %>

<%= f.label :name %>
<%= f.text_field :name %>

Cars

<%= f.fields_for :cars do |car_fields| %>


<%= car_fields.label :color %>

<%= car_fields.text_field :color %>

<% end %>

=======

<%= f.fields_for :cars do |car_fields| %>


<%= car_fields.label :plate %>

<%= car_fields.text_field :plate %>

<% end %>

<%= f.submit %>
<% end %>

http://localhost:8081/owners/new

…

Cars

<div class="field">
  <label for="owner_cars_attributes_0_color">Color</label><br />
  <input id="owner_cars_attributes_0_color"

name=“owner[cars_attributes][0][color]” size=“30” type=“text” />

=======

<div class="field">
  <label for="owner_cars_attributes_1_plate">Plate</label><br />
  <input id="owner_cars_attributes_1_plate"

name=“owner[cars_attributes][1][plate]” size=“30” type=“text” />

…

2

I solved this using content_for. I put everything in the first
fields_for but the fields I wanted to move to a different partial, I
placed in the content_for block. See the example below.

Hope this helps,

Matt

example

<%= f.fields_for :cars do |car_fields| %>


<%= car_fields.label :color %>

<%= car_fields.text_field :color %>


<% content_for :plate_fields do %>

<%= car_fields.label :plate %>

<%= car_fields.text_field :plate %>


<% end %>
<% end %>

=======
<%# This can go anywhere… i.e. another partial %>
<%= content_for :plate_fields %>