I am using Ruby on Rails 3.0.7 and I would like to use check box fields in my view files (that is, for new and edit forms) with an :has_many :through
Record Ass
The link Dogbert supplied is a good way of doing it manual. If you however decide to use Simple Form you get that functionality build in.
Using the example from the previously mentioned article you would do:
<%= simple_form_for(@user) do |f| %>
<%= f.association :groups, :as => :check_boxes %>
<%= f.submit %>
<% end %>
This example is of course very simplified but it should work. Good luck!