IMPORTANT Version 0.6 might break some behaviour from 0.5 and lower versions, please refer to the changelog


Opinio is an engine used to add comments behaviour to your application. The engine is designed to work only with *Rails 3*


Simply add the following line to your Gemfile:

gem "opinio"

and run:



Opinio provides generators to facilitate it's usage. The most common way to quickly get Opinio working is:

rails g opinio:install comment

This will generate the Comment model, migration and also generate the opinio initializer for customization of the engine. A opinio_model will be added on the routes.rb. This method adds the default urls for the model that will act as the comment in your app.

In order to add the comments functionality to a model, you use the opinio_subjectum method

class Post < ActiveRecord::Base

On the routes.rb you should simply add an opinio for your commentable resource

resources :posts do

To render the comments in your views, there is a helper to display the resource's comments easily:

<%= comments_for @post %>

This will render the comments and a form for new comment submissions. Alternatively you can render just the comments or just the form like this:

<%= render_comments @post %>
<%= render_comments_form @post %>

If you need to render the comments with a specific page or limit you can use Kaminari's configurations like paginates_per 10 on your comment model or you can customize it for specific views on the helpers

<%= render_comments @post, :page => params[:page], :limit => 5 %>

This options can also be used on the comments_for helper.



Of course you will want to customize how the comments are displayed or any other customization to the view. To generate the view files on your application, run:

rails g opinio:views

And you can customize all the views used by the engine.


Opinio Model

You can customize the opinio model to suit your needs. The basic customization is the owner class name. It defaults to User but you can change that in the initializer or in the model by passing the :owner_class_name => “MyOwnerClass” option to the opinio_model method call.

Another customization you can do is set the counter_cache to true in the commentable model. You can use the :counter_cache option for that.

The other two customizations are only made through the initializer, and they are the accept_replies which defaults to true and strip_html_tags_on_save which also defaults to true.

Validations on the opinio model are very basic, just ensuring it has a body, a commentable and an owner, if you want any other kind of validation, like the minimum size of a comment, you can use the regular AR validations as you wish.

Remember that if you use titles, you need to add that to your comments table, since the generator doesn't add it by default.

Opinio Subjectum

To change how the models that actually have the comments, you can customize them with any option you would use to a regular has_many relationship in ActiveRecord.

The default options are these:

has_many :comments,
         :class_name => Opinio.model_name,
         :as => :commentable,
         :order => "created_at #{Opinio.sort_order}"),
         :dependent => :destroy

The sort_order and model_name are both setup in the initializer. Here you can do things like, let's say you have moderation in your comments, you can only show the approved comments:

opinio_subjectum :conditions => ["approved = ?", true]

Remember you can override any of these options (except as) by passing them to the opinio_subjectum method.

Pretty Urls

Often times you will want the engine to show the index of comments for a specific item without having to pass the :commentable_type or :commentable_id parameters.

In order to do that, opinio provides a method to ActionController::Base:

opinio_identifier do |params|
  next Review.find(params[:review_id]) if params[:review_id]
  next Product.find(params[:product_id]) if params[:product_id]

Note: you use next instead of return because it is a proc that will be executed later on, and you cannot return on procs

Basically on this method you receive the params variable and you tell the engine, who owns the comments from that page. This allows you to use routes like:


Without passing those 2 parameters. I suggest you put this method on the ApplicationController

Customize destroy conditions

By default, noone can destroy a comment in the engine. You have to tell the engine who can do it. To setup a custom destroy condition use the methods provided by opinio in our controllers. For instance, if our opinio model is called 'comment' it could be written like this:

comment_destroy_conditions do |comment|
  comment.owner == current_user

This would make users only be able to remove their own comments. Another example would be using the CanCan:

comment_destroy_conditions do |comment|
  authorize :destroy, comment

You get the picture, you're inside your controller's methods on that block so you can call anything your normal controllers call on actions.


Opinio provides a few shared examples for testing of your model with rspec On your opinio model test case you can require opinio's shared examples and use them

require 'opinio/shared_examples'

describe Comment do
  it_should_behave_like :opinio

describe Post do
  it_should_behave_like :opinio_subjectum


If you want to help in any way with Opinio please message me or fork the project, make the changes and send me a pull request. For issues please use the github issues tracker


* Refactor the +comments_for+ helper
* Extract documentation to wiki
* Add mongoid support