Question

I have two models – Client & Topic, with a HABTM relationship between them.

I am trying to generate a series of checkboxes of the topics, on the Client form partial.

This is what I am doing:

<% Topic.all.each do |topic| %>
  <% checked = @client.topics.include?(topic) %>
    <%= f.label(:name, topic.name) %> <%= f.check_box @topics, topic.id %>
<% end %>

This is the error I get:

undefined method `merge' for 1:Fixnum

I know one solution is to use check_box_tag, but that forces me to do the record updating of the associations manually.

So I would rather use the form_helper for the checkbox tag. The docs are a bit confusing to me.

How can I get this to work with f.check_box.

Thanks.

Answer 1

For whatever reason, the form helper doesn’t work with check_box.

So, this is the code that works:

<%= check_box_tag "client[topic_ids][]", topic.id, checked %>

According to other answers for similar questions, the helper f.check_box is model bound and the value supplied to the checkbox is implicit from the model on the form. The issue is, I can’t figure out how to get the implicit value of the form_helper to produce the correct tag – i.e. client[topic_ids][], so I have had to resort to check_box_tag.