shw.html.erb

<h1><%= @post.title %></h1>
<p><%= @post.body %></p>

<hr>

<%= link_to "Edit", edit_post_path(@post), :class => 'btn btn-default' %>
<%= link_to "Delete", post_path(@post),
                        method: :delete,
                        data: {confirm: 'Are you sure? '},
                        :class => 'btn btn-danger' %>
<hr>
<h3>Adicionar Commentário</h3>

<%= form_for([@post, @post.comments.build]) do |f| %>
    <p>
     <%= f.label :usuário %><br>
     <%= f.text_field(:username, {:class => 'form-control'})%>
    </p>
    <p>
    <%= f.label :comentário %><br>
    <%= f.text_area(:body, {:class => 'form-control'}) %>
    </p>
    <p>
    <%= f.submit(:Comentar, :class => 'btn btn-primary')%>
    </p>
<% end %>

<h3>Comentários</h3>
<% @post.comments.each do |comment| %>
    <div class="well">
        <p><strong><%= comment.username %></strong>: <%= comment.body %>
        <%= link_to "[X]",
                [comment.post,comment],
                    method: :delete,
                    data: { confirm: 'Are you sure?' }%></p>
    </div>
<% end %>