app/views/categories/index.html.erb
<div class="page-header">
<h1><%= Category.model_name.human(count: 2).capitalize %></h1>
</div>
<p class="pull-right"><%= t('app.counts.category', count: @categories.size).html_safe %></p>
<table class="table table-striped">
<thead>
<tr>
<th><%= Category.human_attribute_name :name %></th>
<th><%= Category.human_attribute_name :children %></th>
</tr>
</thead>
<tbody>
<% @categories.select(&:main?).each do |category| %>
<tr>
<td><%= link_to category.name, category %></td>
<td>
<% category.children.each do |subcategory| %>
<ul class="unstyled">
<li><%= link_to subcategory.name, subcategory %></li>
</ul>
<% end %>
</td>
</tr>
<% end %>
</tbody>
</table>