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A Rails engine for comments.
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Commontator is a Rails engine for comments. It is compatible with Rails 5.2+. Being an engine means it is fully functional as soon as you install and configure the gem, providing models, views and controllers of its own. At the same time, almost anything about it can be configured or customized to suit your needs.


Follow the steps below to install Commontator:

  1. Gem

Add this line to your application's Gemfile:

gem 'commontator'

You will also need jquery and a sass compiler, which can be either be installed through the webpacker gem and yarn/npm/bower or through the jquery-rails and sass[c]-rails gems:

gem 'jquery-rails'
gem 'sassc-rails'

Then execute:

$ bundle install
  1. Initializer and Migrations

Run the following command to copy Commontator's initializer and migrations to your app:

$ rake commontator:install

Or alternatively:

$ rake commontator:install:initializers

$ rake commontator:install:migrations

And then execute:

$ rails db:migrate
  1. Configuration

Change Commontator's configurations to suit your needs by editing config/initializers/commontator.rb. Make sure to check that your configuration file is up to date every time you update the gem, as available options can change with each minor version. If you have deprecated options in your initializer, Commontator will issue warnings (usually printed to your console).

Commontator relies on Rails's sanitize helper method to sanitize user input before display. The default allowed tags and attributes are very permissive, basically only blocking tags, attributes and attribute values that could be used for XSS. Read more about configuring the Rails sanitize helper..

  1. Routes

Add this line to your Rails application's routes.rb file:

mount Commontator::Engine => '/commontator'

You can change the mount path if you would like a different one.


  1. Javascripts

Make sure your application.js requires jquery and rails-ujs or jquery-ujs:

Rails 5.1+:

//= require jquery
//= require rails-ujs

Rails 5.0:

//= require jquery
// If jquery-ujs was installed through jquery-rails
//= require jquery_ujs
// If jquery-ujs was installed through webpacker and yarn/npm/bower
//= require jquery-ujs

If using Commontator's mentions functionality, also require Commontator's application.js:

//= require commontator/application
  1. Stylesheets

In order to display comment threads properly, you must require Commontator's application.scss in your application.[s]css:

*= require commontator/application

Sprockets 4+

You must require Commontator's manifest.js in your app's manifest.js for images to work properly:

//= link commontator/manifest.js

You also need to either add the necessary link tag commands to your layout to load commontator/application.js and commontator/application.css or require them in your app's application.js and application.css like in Sprockets 3.


Follow the steps below to add Commontator to your models and views:

  1. Models

Add this line to your user model(s) (or any models that should be able to post comments):


Add this line to any models you want to be able to comment on (i.e. models that have comment threads):


if you want the thread and all its comments removed when your commontable model is destroyed pass :destroy as the :dependent option toacts_as_commontable:

acts_as_commontable dependent: :destroy

instead of :destroy you may use any other supported :dependent option from rails has_one association.


In the following instructions, @commontable is an instance of a model that acts_as_commontable. You must supply this variable to the views that will use Commontator.

Wherever you would like to display comments, call commontator_thread(@commontable):

<%= commontator_thread(@commontable) %>

This will create a link that can be clicked to display the comment thread.

Note that model's record must already exist in the database, so do not use this in new.html.erb, _form.html.erb or similar views. We recommend you use this in the model's show.html.erb view or the equivalent for your app.

  1. Controllers

By default, the commontator_thread method only provides a link to the desired comment thread. Sometimes it may be desirable to have the thread display right away when the corresponding page is loaded. In that case, just add the following method call to the controller action that displays the page in question:


Note that the call to commontator_thread in the view is still necessary in either case.

The commontator_thread_show method checks the current user's read permission on the thread and will display the thread if the user is allowed to read it, according to the options in the initializer.

That's it! Commontator is now ready for use.


When you enable subscriptions, emails are sent automatically by Commontator. If sending emails, remember to add your host URL's to your environment files (test.rb, development.rb and production.rb):

config.action_mailer.default_url_options = { host: "" }

Sometimes you may need to subscribe (commontator) users automatically when some event happens. You can call object.commontator_thread.subscribe(user) to subscribe users programmatically. Batch sending through Mailgun is also supported and automatically detected. Read the Customization section to see how to customize subscription emails.


You can allow users to vote on each others' comments by adding the acts_as_votable gem to your Gemfile:

gem 'acts_as_votable'

And enabling the relevant option in Commontator's initializer:

config.comment_voting = :ld # See the initializer for available options


You can allow users to mention other users in the comments. Mentioned users are automatically subscribed to the thread and receive email notifications.

First make sure you required Commontator's application.js in your application.js as explained in the Javascripts section. Then enable mentions in Commontator's initializer:

config.mentions_enabled = true

Finally configure the user_mentions_proc, which receives the current user, the current thread, and the search query inputted by that user and should return a relation containing the users that can be mentioned and match the query string:

config.user_mentions_proc = ->(current_user, thread, query) { ... }

Please be aware that with mentions enabled, any registered user can use the user_mentions_proc to search for other users. Make sure to properly escape SQL in this proc and do not allow searches on sensitive fields.

Use '@' with at least three other characters to mention someone in a new/edited comment.

The mentions script assumes that Commontator is mounted at /commontator, so make sure that is indeed the case if you plan to use mentions.

Browser Support

Commontator should work properly on any of the major browsers. The mentions functionality won't work with IE before version 8. To function properly, this gem requires that visitors to the site have javascript enabled.


Copy Commontator's files to your app using any of the following commands:

$ rake commontator:copy:locales

$ rake commontator:copy:images
$ rake commontator:copy:javascripts
$ rake commontator:copy:stylesheets

$ rake commontator:copy:views
$ rake commontator:copy:helpers

$ rake commontator:copy:controllers
$ rake commontator:copy:mailers

$ rake commontator:copy:models

You are now free to modify them and have any changes made manifest in your application. You can safely remove files you do not want to customize.

You can customize subscription emails (mailer views) with rake commontator:copy:views.

If copying Commontator's locales, please note that by default Rails will not autoload locales in subfolders of config/locales (like ours) unless you add the following to your application.rb:

config.i18n.load_path += Dir[root.join('config', 'locales', '**', '*.yml')]


  1. Fork the lml/commontator repo on Github
  2. Create a feature or bugfix branch (git checkout -b my-new-feature)
  3. Write tests for the feature/bugfix
  4. Implement the new feature/bugfix
  5. Make sure both new and old tests pass (rake)
  6. Commit your changes (git commit -am 'Added some feature')
  7. Push the branch (git push origin my-new-feature)
  8. Create a new Pull Request to lml/commontator on Github

Development Environment Setup

  1. Use bundler to install all dependencies:
$ bundle install
  1. Setup the database:
$ rails db:setup


To run all existing tests for Commontator, simply execute the following from the main folder:

$ rake


This gem is distributed under the terms of the MIT license. See the MIT-LICENSE file for details.