## post/show (posts_controller.rb) [ruby_on_rails]
def show
  @post = Post.find(params[:id])
  @comments = @post.comments

  respond_to do |format|
    format.html # show.html.erb
    format.xml  { render :xml => @post }
  end
end

## comment/create (comments_controller.rb) [ruby_on_rails]
def create
  @post = Post.find(params[:post_id])
  @comment = @post.comments.build(params[:comment])

  if @comment.save
    redirect_to @post
  else
    # need to create an empty views/comments directory so it can go back a level into the posts
    render :action => "../posts/show"
  end
end

## form_for @comment (posts/show.html.erb) [html_rails]
<% form_for @post.comments.build, :url => post_comments_path(@post) do |f| %>
  <p><%= f.error_messages %></p>
  <p><%= f.text_area :body %></p>
  <p><%= f.submit "Add comment" %></p>
<% end %>

## list current comments (posts/show.html.erb) [html_rails]
<% @comments.each do |comment| %>
  <p>
    <b>Posted <%= time_ago_in_words(comment.created_at) %> ago</b><br/>
    <%= comment.body %>
  </p>
<% end %>