RAILS HABTM checkboxes don't update

Question

I am trying to realize HABTM checkboxes following this tutorial: http://www.justinball.com/2008/07/03/checkbox-list-in-ruby-on-rails-using-habtm/

While everything seems to work nicely the updates are not saved to my database. My controller looks like the following:

class UserrolesController < ApplicationController

 before_action :set_userrole

 def edit
   @projects=Project.all
 end

 def update
    params[:userrole][:project_ids] ||= []
    @userrole = Userrole.find(params[:id])
    if @userrole.update_attributes(userrole_params)
        flash[:notice] = "Settings have been saved."
        redirect_to edit_userrole_url(@userrole)
    else
        flash.now[:error] = @userrole.errors
        setup_form_values
        respond_to do |format|
            format.html { render :action => :edit}
        end
    end
 end

 private

 def set_userrole
   @userrole = Userrole.find(params[:id])
 end

 def userrole_params
   params.require(:userrole).permit(:name, :project_ids)
 end

end

My _form.html.erb like this:

<%= form_for(@userrole) do |f| %>
<% if @userrole.errors.any? %>
<div id="error_explanation">
  <h2><%= pluralize(@userrole.errors.count, "error") %> prohibited this person from being saved:</h2>

  <ul>
  <% @userrole.errors.full_messages.each do |msg| %>
    <li><%= msg %></li>
  <% end %>
  </ul>
</div>
<% end %>

<div class="center">
  <div class="field">
    <%= f.label :Name %>
<%= f.text_field :name %>
 </div>

<ul class="checkbox-list">
  <% @projects.each do |project| -%>
<li><%= check_box_tag "userrole[project_ids][]", project.id, userrole_edits_project?(project) -%> <%= project.name -%></li>
  <% end -%>
</ul>

 <div class="actions">
   <%= f.submit "Speichern", class: "btn btn-primary" %>
 </div>
</div>
<% end %>

So I did everything like in the tutorial, the :name is saved without any problems, but the ids are not saved to the database. There is no error message. Does anybody has an idea what might go wrong? Maybe some missing permission somewhere?

Answer 1

So finally I found a work around for this problem. I forced the update of project_ids by adding the following line in def update:

    @userrole.project_ids=params[:userrole][:project_ids]