Adding AJAX 'Post a Comment' to blog

I am working a blog system for my girlfriend, and am trying to add
AJAX to many places throughout the blog where refreshing is most
troublesome; like when visitors post comments!

Basically I have a text area for the comment and a submit button, what
I want to do is obviously only refresh the <div> which contains the
current comments when a user submits their comment.

I thought I had figured it out, however when a user posts a comment
the comment_list div shows empty until the page is refreshed :frowning:

Here is the add_comment action in my controller:

  def add_comment
    Post.find(params[:id]).comments.create(params[:comment])
  end

And here is my show.rhtml which shows the blog post + comments and
comment form :

<%= javascript_include_tag "prototype" %>

<%= render :partial => "post", :object => @post %>

<%= link_to 'Edit', :action => 'edit', :id => @post %> |
<%= link_to 'Back', :action => 'list' %>

<h2>Comments</h2>

<div id='comment_list'>
<% for comment in @post.comments %>
  <%= comment.body %>
  <hr />
<% end %>
</div>

<% form_remote_tag :url => { :action => "add_comment", :id =>
@post }, :html => {:name => 'add_comment_form'}, :update =>
'comment_list', :success => visual_effect(:highlight, "comment_list")
do %>
  <%= text_area "comment", "body" %> <br />
  <%= submit_tag "Comment!" %>
<% end %>

Also I had to create a blank add_comment.rhtml view otherwise I kept
getting template errors.

Anyone got any suggestions/ideas?

Worked a treat thanks!