app/views/answers/_viewer.html.erb
<div class="row">
<div class="viewer">
<!-- サムネイル -->
<div class="col-md-3 visible-md visible-lg">
<div class="thumbs">
<!-- 並び替え用フォーム -->
<%= form_for @answer do |f| %>
<ol>
<!-- 個別のファイル -->
<%= f.fields_for :answer_files do |file_form| %>
<li>
<% if can? :update, @answer %>
<%= link_to answer_answer_file_path(@answer, file_form.object),
method: :delete, data: { confirm: 'この画像を削除してもよろしいですか?' } do %>
<i class="fa fa-trash-o"></i>
<% end %>
<% end %>
<%= file_form.hidden_field :order %>
<a href="#file_<%= file_form.object.id %>">
<% if file_form.object.is_pdf? %>
PDF
<% else %>
<%= image_tag file_form.object.image.url %>
<% end %>
</a>
</li>
<% end %>
</ol>
<% end %>
</div>
</div>
<!-- メイン -->
<div class="col-md-9">
<div class="preview">
<% @answer_files.each do |file| %>
<% if file.is_pdf? %>
<%= link_to file.image.url, id: "file_#{file.id}", class: 'btn btn-primary' do %>
PDFを開く
<% end %>
<% else %>
<%= image_tag file.image.url, id: "file_#{file.id}" %>
<% end %>
<% end %>
</div>
</div>
<% if @answer.answer_text.present? %>
<div class="answer_text">
<%= markdown(@answer.answer_text) %>
</div>
<% end %>
</div>
</div>