gistfile1.rb

# PRODUCT MODEL
has_many :product_people
has_many :people, :through => :product_people

accepts_nested_attributes_for :people

<%= f.inputs "Cast" do %>
  <%= f.inputs :for => :people do |p| %>
    <%= p.input :name %>
    <%= p.input :_destroy, :as => :boolean %>
  <% end %>
<% end %>