Using the acts_as_tree plugin should make this fairly easy to implement. Install it using
ruby script/plugin install acts_as_tree
app/models/comment.rb
class Comment < ActiveRecord::Base
acts_as_tree :order => 'created_at'
end
db/migrate/20090121025349_create_comments.rb
class CreateComments < ActiveRecord::Migration
def self.up
create_table :comments do |t|
t.references :parent
t.string :title
t.text :content
...
t.timestamps
end
end
def self.down
drop_table :comments
end
end
app/views/comments/_comment.html.erb
<div id="comment_<%= comment.id %>">
<h1><%= comment.title %>
<%= comment.content %>
<%= render :partial => 'comments/comment', :collection => comments.children %>
</div>
app/views/comments/show.html.erb
<div id="comments">
<%= render :partial => 'comments/comment', :object => Comment.find(params[:id]) %>
</div>
The magic happens in show.html.erb when it calls <%= render :partial => 'comments/comment', :object => Comment.find(params[:id]) %>, this will cause the partial to recursively render all children comments. If you want a limit to the depth, you can do it in the partial or in the model.
Edit:
This will leave you with all the comments with the same spacing in the HTML for every depth. If you want to produce easy to read HTML, just use render(...).gsub(/^/, "\t") this will work recursively as well producing nicely indented HTML.
I combined it into my own method in app/helpers/application_helper.rb
def indented_render(num, *args)
render(*args).gsub(/^/, "\t" * num)
end
So now you can call <%= indented_render 1, :partial => 'comments/comment', ... %>