app/views/categories/index.html.erb
<div class="card">
<header class="card-header d-flex align-items-center">
<h3 class="mr-auto">Categories</h3>
<% if policy(:category).new? %>
<%= link_to '+ New', new_category_path, class: "btn btn-primary" %>
<% end %>
</header>
<section>
<table class="table">
<thead>
<tr>
<th scope="col">Name</th>
<th scope="col">Description</th>
<th scope="col"></th>
</tr>
</thead>
<tbody>
<% @categories.includes(:subcategories).each do |category| %>
<%= render 'category', category: category %>
<% end %>
</tbody>
</table>
</section>
</div>