Find version where specific attribute has changed in papertrail

Well, I've concluded this is not possible out-of-the-box in paper_trail.

What I ended up doing was, when one of the specific attributes was updated, save a flag in a separate metadata column in the Versions table.

Then I can search against these columns in the future to find out when that specific attribute changed.

Hopefully this helps someone else.

Here's another option for those who don't want to use a separate metadata column:

def version_where_attribute_changed_to(attribute_name, attribute_value)
  versions.select do |version|
    object_changes = YAML.load version.object_changes
    (object_changes[attribute_name.to_s] || [])[1] == attribute_value
  end
end

The following gets all the versions where attribute became value (which in most apps is probably around 1):

object.versions.
       map(&:object_changes).
       map{|a| YAML::load a}.
       select{|a| (a[:attribute] || [])[1]=='value'}

Result would be something like:

[{"attribute"=>[nil, "value"],
  "updated_at"=>[2015-01-02 12:20:36 UTC, 2015-01-02 12:20:56 UTC]}]

The updated_at[1] value indicates when attribute became value.

Getting the id of the Version can be built upon the provided code snippet.