使用paper_trail gem创建审核跟踪

Question

I'm pretty new to rails, and brand new to using the paper_trail gem.

I would like to show a list of each change made to the location or tag number of my assets model. I have installed paper_trail and it seems to be working correctly. In my view I have this:

<% @asset.versions.order('created_at DESC').each do |version| %>
    On <%= version.created_at %> <%= version.whodunnit %> updated this asset.<br>
    <ul>
        <li>Asset relocated from "<%= version.last.locaton %>" to "<%= version.location %> "</li>
        <li>User changed from "<%= version.last.tag_number %>" to "<%= version.tag_number %> "</li>
    </ul>
<% end %>

This gives me the correct information for when the change was made and who made it, but I cannot figure out to display the lines that say (for instance): Asset relocated from "223" to "258 or Tag Number changed from "1173" to "1175".

Ideally I would only show information for things that have changed. So if the location changed but the tag number did not, I would show only the location line.

I don't really even know where to start. Any help would be appreciated. Thanks!

Answer 1

From The PaperTrail Documentation: PaperTrail has an optional table column that can be used when creating versions called object_changes . This will store ONLY the changes made between versions. Which will allow you to just display the changes between each version. It works like this.

>> widget = Widget.create :name => 'Bob'
>> widget.versions.last.changeset                # {'name' => [nil, 'Bob']}
>> widget.update_attributes :name => 'Robert'
>> widget.versions.last.changeset                # {'name' => ['Bob', 'Robert']}
>> widget.destroy
>> widget.versions.last.changeset                # {}

If you recently added paper_trail to your model then you can run a migration to add this column. This will track future changes.

class AddObjectChangesColumnToVersions < ActiveRecord::Migration
  def self.up
    add_column :versions, :object_changes, :text
  end

  def self.down
    remove_column :versions, :object_changes
  end
end

I recently had a need to get the changes, however, we have years of version data for 20+ models and adding that migration would only help in the future and not give me all of the data changes in the past.

I wound up creating a patch for PaperTrail that added methods like diff_previous , diff_next , diff_live which would give me the difference between versions. It was based off the idea of this patch of paper_trail( https://github.com/jeremyw/paper_trail/blob/master/lib/paper_trail/has_paper_trail.rb#L151-L156 ) but I implemented it quite differently. If you want more details I will see if I can open source that patch.