Rails 4 - checkboxes for has_and_belongs_to_many association

Question

I recently had a problem getting checkboxes to work for a has_and_belongs_to_many (HABTM) association in Rails 4. I was able to find the information on how to get it working correctly in a few disparate places, but thought it would be good to document the few simple steps necessary to get it working correctly in one place here on StackOverflow.

As a setup assume a model of Kennel with a HABTM association to Handler.

class Kennel
    has_and_belongs_to_many :handlers
end

Answer 1

This is all you need to do for the form: Don't do it manually when there is a built in helper.

<%= form_for @kennel do |f| %>
  <%= f.collection_check_boxes(:handler_ids, Handler.all, :id, :to_s) %>
<% end %>