fields_for.html.erb

<%= f.nested_fields_for :evaluations, wrapper_tag: :tr, wrapper_options: { class: 'fields' } do |fn| %>
  <% if ( !fn.object.skill.blank? && fn.object.skill.type == 'critical factors' ) %>
    <tr>
      <%= fn.input :skill_id, as: :hidden, input_html: { value: fn.object.skill.id } %>
        <td><%= fn.object.skill.name %></td>
        <td><%= fn.association :grade, collection: @evaluation_grades, label: false %></td>
    </tr>
  <% end %>
<% end %>