gistfile1.rb

# MODEL
class Vocabulary < ActiveRecord::Base
  has_many :terms, :dependent => :destroy
  accepts_nested_attributes_for :terms,
                                :allow_destroy => true,
                                :reject_if => proc { |attrs| attrs[:name].blank? }

end


# HELPER
module VocabulariesHelper
  def setup_vocabulary(vocabulary)
    returning(vocabulary) do |v|
      3.times { v.terms.build }
    end
  end
end


# VIEW
<% form_for setup_vocabulary(@vocabulary), :html => { :class => "std-form short" } do |f| %>
  
  <%= f.error_messages %>

  <p>
    <%= f.label :title %>
    <%= f.text_field :title, :class => 'text' %>
  </p>
  
  <fieldset id="terms">
    <legend>Terms:</legend>
    <% f.fields_for :terms do |term_form| %>
      <div class="term">
        <p>
          <%= term_form.label :name, "Term:" %>
          <%= term_form.text_field :name, :class => 'text' %>
          <% unless term_form.object.new_record? %>
            <%= term_form.check_box '_delete' %>
            <%= term_form.label '_delete', 'Remove' %>
          <% end %>
        </p>
      </div>
    <% end %>
  </fieldset>
  
  <p>
    <%= f.submit @vocabulary.new_record? ? "Create" : "Update" %>
  </p>
<% end %>