Question

Event saves the section id’s in an array. But in the /events/1/edit view for a newly created event, the expected checkboxes are not checked. I’m guessing because the default for checkbox values is booleans.

Event.last.newsletters #=> ["108", "115", "116", "117", "118", ""]

I have a CRUD for Event. Each Event can belong to multiple Sections. I have this displayed as a collection of checkboxes with the simpleform gem.

<%= simple_form_for @event do |f| %>
...
<%= f.collection_check_boxes :newsletters, Section.all, :id, :name, :input_html => { :class => 'checkbox' } %>

This results in the following html:

<span><input id="event_newsletters_1" name="event[newsletters][]" type="checkbox" value="1" /><label class="collection_check_boxes" for="event_newsletters_1">Newsletter 1</label></span>
<span><input id="event_newsletters_2" name="event[newsletters][]" type="checkbox" value="2" /><label class="collection_check_boxes" for="event_newsletters_2">Newsletter 2</label></span>
etc. etc.

When I create a new event or edit an event, the newsletter values are saved properly in the model.

Answer 1

Try specify the param :checked:

<%= f.collection_check_boxes :newsletters,
                             Section.all,
                             :id,
                             :name,
                             :input_html => { :class => 'checkbox' },
                             :checked => @event.newsletters %>

Reference: how to preselect an association checkbox using simple_form