How does one pre-fill a has_many collection using Hobo?

Question

I have an order entry-like system where we know most of the time we'll need to use most items in the product catalog. The models are:

class Product < ActiveRecord::Base
  hobo_model
  fields do
    name :string
  end
end

class Order < ActiveRecord::Base
  hobo_model
  fields do
    ship_to :text
  end
  has_many :order_lines
end

class OrderLine < ActiveRecord::Base
  hobo_model
  fields do
    quantity :integer, :null => false, :default => 0
  end

  belongs_to :product
  belongs_to :order
end

In the controller, I'm doing:

class OrdersController < ApplicationController
  hobo_model_controller
  auto_actions :all

  def new
    hobo_new do
      Product.all.each do |product|
        @order.order_lines.build :product => product
      end
    end
  end
end

When rendering new.dryml, it's as if the order lines didn't exist. We know the number of products (3) and we know we want a line for each of them. There's more backend code that'll eliminate the rows which have 0 quantity.

How do I make it so the form opens with a row per product being on-screen?