Auditing via paper_trail (change history)

paper_trail is a gem used for auditing and versioning 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 and the before_action :set_paper_trail_whodunnit (see https://git.io/vrTsk why you need to do this). (optional)

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

  # ...
  protected

  def user_for_paper_trail
    admin_user_signed_in? ? current_admin_user.try(:id) : '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 PaperTrail::Version.order('id desc').limit(20) do # Use PaperTrail::Version if this throws an error
    column ("Item") { |v| v.item }
    # column ("Item") { |v| link_to v.item, [:admin, v.item] } # Uncomment to display as link
    column ("Type") { |v| v.item_type.underscore.humanize }
    column ("Modified at") { |v| v.created_at.to_s :long }
    column ("Admin") { |v| link_to AdminUser.find(v.whodunnit).email, [:admin, AdminUser.find(v.whodunnit)] }
  end
end

Linking to model

To link the item column to your model in active_admin use:

column ("Item") do |v| 
    if v.item
        link_to v.item, [:admin, v.item]
    end
end

Versioning models

in app/admin/posts.rb:

controller do
  def show
      @post = Post.includes(versions: :item).find(params[:id])
      @versions = @post.versions 
      @post = @post.versions[params[:version].to_i].reify if params[:version]
      show! #it seems to need this
  end
end
  sidebar :versionate, :partial => "layouts/version", :only => :show

then create the partial in app/views/layouts/_version.html.erb with this:

<% if !@versions.empty? %>
  <h3>Current Version: <%= @versions.length %></h3>

  <b>Created At:</b>
  <%= @versions.last.created_at%>
  <br>
  <b>Admin</b>: <%= AdminUser.find(@versions.last.whodunnit).email %>
  <br>
  <% if @versions.length.to_i > 1 %>
    <% if params[:version].to_i > 1 || !params[:version] %>
      <%= link_to "Previous version", {:version => (params[:version] || @versions.length).to_i - 1}%>
      <br>
    <% end %>
    <% if params[:version] %>
      <h3>This is <%= "#{params[:version]}"%> version</h3>

      <b>Modify at:</b>
      <%= @versions[(params[:version].to_i - 1)].created_at %>
      <br>
      <b>Admin</b>:
      <%= AdminUser.find(@versions[(params[:version].to_i - 1)].whodunnit).email %>
      <br>

      <%= link_to "Go to current version"%>
    <% end %>
  <% end %>
<% else %>
  <p>This item does not have any registered version.</p>
<% end %>

###Adding a history page. you can add it by including a member action. like this in admin/posts.rb add

...
  member_action :history do
    @post = Post.find(params[:id])
    @versions = @post.versions
    render "layouts/history"
  end
...

Then create the file app/views/layouts/history.html.arb with

panel "Historia" do
  table_for assigns[:versions]
end

Visit /admin/post/:id/history to see history for a particular post.