Rails Nested Attributes Doesn't Insert ID Correctly

I'm attempting to edit a model's nested attributes, much as outline here, replicated here:

    <%= form_for @person do |person_form| %>
      <%= person_form.text_field :name %>
      <% for address in @person.addresses %>
        <%= person_form.fields_for address, :index => address do |address_form|%>
          <%= address_form.text_field :city %>
        <% end %>
      <% end %>
    <% end %>

In my code, I have the following:

<%= form_for(@meal) do |f| %>
  <!-- some other stuff that's irrelevant... -->

      <% for subitem in @meal.meal_line_items %>
         <!-- # Edit 2: I need to display information here about开发者_如何学运维 the subitem
              Which I can't find a way to pass it to the partial, or work in 
              this manner for existing items
         -->
         <%= subitem.food.name %>
         <%= subitem.food.calories %>

         <%= f.fields_for subitem, :index => subitem do |line_item_form| %>
            <%= line_item_form.label :servings %><br/>
            <%= line_item_form.text_field :servings %><br/>
            <%= line_item_form.label :food_id %><br/>
            <%= line_item_form.text_field :food_id %><br/>
         <% end %>
      <% end %>

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

This works great, except, when I look at the HTML, it's creating the inputs that look like the following, failing to input the correct id and instead placing the memory representation(?) of the model. As a result, an update fails:

<input type="text" value="2" size="30" name="meal[meal_line_item][#<MealLineItem:0x00000005c5d618>][servings]" id="meal_meal_line_item_#<MealLineItem:0x00000005c5d618>_servings">

EDIT: The reason I'm attempting to do it in this method is that I need to gather some information on associations for existing meal_line_items. For example, in the area where I took out code, I have some code to the effect of:

<%= subitem.food.name %>
<%= subitem.food.calories %>

Getting this information won't work if I am using a form builder with partials, at least, not in my trials.

Edit 2:* See the edit in the code. Here's my MealLineItem

class MealLineItem < ActiveRecord::Base
  # Associations ---------------------
  belongs_to :food
  belongs_to :meal
end

And meal accepts_nested_attributes for the model. As you can see it belongs to both food and meal model. For the existing meal_line_item I need to do something like:

meal_line_item.food.name

Is there f. missing from <%= fields_for?

--edit

Have you tried:

<%= f.fields_for 'meal[meal_line_item][]', subitem do |line_item_form| %>

--edit

Docs say that it should work without loop too:

<%= form_for(@meal) do |f| %>
  <!-- some other stuff that's irrelevant... -->

  <%= f.fields_for :meal_line_items do |line_item_form| %>
    <%= line_item_form.label :servings %><br/>
    <%= line_item_form.text_field :servings %><br/>
    <%= line_item_form.label :food_id %><br/>
    <%= line_item_form.text_field :food_id %><br/>
  <% end %>

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

Have to test this but maybe this approach?

_form

<%= form.fields_for :meal_line_items do |meal_line_item_form| %>
 <% @meal.meal_line_items.each do |meal_line_item| %>
  <%= render :partial => "meal_line_items/meal_line_item", :locals => { :meal_line_item_form => meal_line_item_form, :meal_line_item => meal_line_item } %>
 <% end %>
<% end %>

meal_line_items/_meal_line_item.erb

<%= meal_line_item_form.label :servings %><br/>
<%= meal_line_item_form.text_field :servings %><br/>
<%= meal_line_item_form.label :food_id %><br/>
<%= meal_line_item_form.text_field :food_id %><br/>

EDIT

here's a link to an example for setting the formbuilder iterator directly (Rails 2.3.8 though). The associations between Outbreak -> Incidents -> Location should be similiar to the ones for Meal -> Meal_line_items -> Food.

AJAX update of accepts_nested_attributes_for partials

After searching high and low, I found the error. Although I was modifying the partial and was receiving a NameError it's because I was calling the partial from a helper method - exactly the same problem as stated in the following question:

rails fields_for render partial with multiple locals producing undefined variable