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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 3.1+, 4 and 5. 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.


There are 4 steps you must follow to install commontator:

  1. Gem

Add this line to your application's Gemfile:

gem 'commontator', '~> 5.1.0'

And then execute:

$ bundle install
  1. Initializer and Migration

Run the following command to copy commontator's initializer and migration to your app:

$ rake commontator:install

Or alternatively:

$ rake commontator:install:initializers

$ rake commontator:install:migrations

And then execute:

$ rake 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).

  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. Stylesheets

In order to display comment threads properly, you must add the following to your application.css:

*= require commontator/application


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 raise a Commontator::SecurityTransgression exception if the user is not allowed to read it, according to the options in the initializer. It is up to you to ensure that this method is only called if the user is authorized to read the thread.

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: "" }

Batch sending through Mailgun is also supported and automatically detected.

You may need to customize the mailer views with rake commontator:copy:views though only app/views/commontator/subscriptions_mailer/ may be necessary. These in turn may require that you customize the localizations as well (see below for more details on that).

Sometimes you may need to add users automatically upon some event. For example, you may wish to automatically "subscribe" a (commontator) user to a (commontable) event so they get messages sent to the event automatically after joining the event. To do this you call event.thread.subscribe(user) when adding that user to that event.


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 add the following to your application.js file:

//= require commontator/application

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 to 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:stylesheets

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

$ rake commontator:copy:controllers
$ rake commontator:copy:models

You are now free to modify them and have any changes made manifest in your application.

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's configuration file:

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


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Write tests for your feature
  4. Implement your new feature
  5. Test your feature (rake)
  6. Commit your changes (git commit -am 'Added some feature')
  7. Push to the branch (git push origin my-new-feature)
  8. Create new Pull Request

Development Environment Setup

  1. Use bundler to install all dependencies:
$ bundle install
  1. Load the schema:
$ rake db:schema:load

Or if the above fails:

$ bundle exec rake db:schema:load


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

$ rake

Or if the above fails:

$ bundle exec rake


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

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