Untitled

Using check boxes with a has_many relationship
create_table "invoices" do |t|
end

create_table "lines" do |t|
  t.integer  "invoice_id"
end

class Invoice < ActiveRecord::Base
  has_many :lines
end

class Line < ActiveRecord::Base
  belongs_to :invoice
end

<%= f.input :line_ids, :as => :check_boxes %>

<span>
  <input name="invoice[line_ids][]" type="hidden" value="" />
  <input checked="checked" class="check_boxes optional" id="invoice_line_ids_1" name="invoice[line_ids][]" type="checkbox" value="1" />
  <label class="collection_check_boxes" for="invoice_line_ids_1">Line Name 1</label>
</span>

<span>
  <input name="invoice[line_ids][]" type="hidden" value="" />
  <input checked="checked" class="check_boxes optional" id="invoice_line_ids_2" name="invoice[line_ids][]" type="checkbox" value="2" />
  <label class="collection_check_boxes" for="invoice_line_ids_2">Line Name 2</label>
</span>

<% Line.all.each do |line| %>
  <%= hidden_field_tag "invoice[line_ids][]" %>
  <%= check_box_tag "invoice[line_ids][]", line.id, @invoice.lines.include?(line), :id => "invoice_line_ids_#{line.id}" %>
<% end %>