Rails 2.3 : Nested Attributes / Nested Object Forms

accepts_nested_attributes_for / fields_for
Nested attributes allow you to save attributes on associated records through the parent.
automatic (and atomic) saving of a record together with its associated children, child-aware validations, and support for nested forms.

class Customer < ActiveRecord::Base
  has_many :orders
  accepts_nested_attributes_for :orders, :allow_destroy => true
end

<% form_for @customer do |customer_form| %>
  <%= customer_form.text_field :name %>

  <% customer_form.fields_for :orders do |order_form| %>
    <%= order_form.text_field :number %>

    <% unless order_form.object.new_record? %>
      <%= order_form.check_box :_delete %>
    <% end %>
  <% end %>
  <%= customer_form.submit %>
<% end %>

Ruby on Rails 2.3 Release Notes - 4.1 Nested Attributes
Ruby on Rails 2.3 Release Notes - 6.1 Nested Object Forms
Module: ActiveRecord::NestedAttributes::ClassMethods
Module: ActionView::Helpers::FormHelper
Nested AttributesとNested Model Formsを使って親子オブジェクトを一括で登録/変更するには