Question

This is what I am trying to do:

<% Topic.all.each do |topic| %>
  <%= f.check_box "topic_ids[]", topic.id, false %>
<% end %>

That is inside a form_for.

This is the error I get:

undefined method `merge' for 1:Fixnum

Around the main check_box line.

My Topic model actually looks like this, and I would like for the checkboxes to display the name of the topics on each checkbox:

# Table name: topics
#
#  id         :integer          not null, primary key
#  name       :string(255)

What am I missing?

Answer 1

You should use check_box_tag instead of f.check_box.

check_box_tag "topic_ids[]",topic.id 

The difference is f.check_box is for model-bounded forms and the value supplied to the check box is implicit from the given model and doesn’t need to be provided.