Auditing via paper_trail (change history)

paper_trail is a gem used for auditing and versioning of your models. We can easily use it with active_admin to show a list of recently modified items in the admin screen.

Example:

Integration instructions

1. Install PaperTrail as a gem via your Gemfile:

   gem 'paper_trail'

2. Generate a migration which will add a versions table to your database:

   rails generate paper_trail:install

3. Run the migration:

   rake db:migrate

4. Add user_for_paper_trail to controller so paper_trail knows which user updated the item. (optional)

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  # ...
  protected

  def user_for_paper_trail
    admin_user_signed_in? ? current_admin_user : 'Unknown user'
  end
  # ...
end

5. Add has_paper_trail to the models you want to track:

# app/models/post.rb
class Post < ActiveRecord::Base
  has_paper_trail
  # ...
end

6. Display the versions table on the dashboard

# app/admin/dashboard.rb
section "Recently updated content" do
  table_for Version.order('id desc').limit(20) do
    column "Item" do |v| v.item end
    column "Type" do |v| v.item_type.underscore.humanize end
    column "Modified at" do |v| v.created_at.to_s :long end
    column "Admin" do |v| link_to AdminUser.find(v.whodunnit), admin_admin_path(v.whodunnit) end
  end
end

Linking to model

To link the item column to your model in active_admin, I added the following method to my model:

# app/models/post.rb
class Post < ActiveRecord::Base
  include Rails.application.routes.url_helpers # neeeded for _path helpers to work in models
      
  has_paper_trail
  # ...
  def admin_permalink
    admin_post_path(self)
  end
  # ...
end

Then in app/admin/dashboard.rb:

column "Item" do |v| link_to v.item, v.item.admin_permalink end

Versioning models

TODO