Reddit-style nested/threaded/indented comments for Rails?

Question

I\'m wondering if someone has already built a system for threaded comments (for lack of a better term) in Rails or if I need to build it myself.

In case it\'s not c

Answer 1

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 %></h1>
  <%= 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', ... %>

Edit:
Fixed missing closing </h1> tag in the example.

Answer 2

The links to the ActsAsTree documentation as given by Hector and Samuel seem to be broken. You can get the docs at

 
http://web.archive.org/web/20061011101510/http://wiki.rubyonrails.org/rails/pages/ActsAsTree

(I used a pre tag as the linked kept displaying wrong for some reason).

Answer 3

Did you tried acts_as_tree plugin on your model? It's a official ActiveRecord component.

http://wiki.rubyonrails.org/rails/pages/ActsAsTree

Answer 4

There is a has_threaded_comments gem, never used it, but it looks like it does exactly this: https://github.com/aarongough/has_threaded_comments