Rails Merit Gem, How to display timeline of reputation changes

I'm using the merit gem for rails, and would like to have a timeline of reputation changes, badges earned etc. For example

+1 22Feb PostTitle voted up
+3 22Feb PostTitle favorited
-1 22Feb PostTitle voted down ....and so on.

Based on the readme, I created the following:

config/initializers/merit.rb

config.add_observer 'ReputationChangeObserver'

reputation_change_observer.rb

class ReputationChangeObserver
  def update(changed_data)
    # `changed_data[:description]` holds information on what changed
    # badges granted or removed, points changed.

    # `changed_data[:merit_object]` reputation related object created by merit.
    # It responds to `sash_id` and `sash`. From there you can get to your
    # application object that had it's reputation changed, for example:
    # sash_id = changed_data[:merit_object].sash_id
    # User.where(sash_id: sash_id).first

    # You may use this to fill a timeline with notifications for users, send
    # emails, etc.

  end
end

Question is, what next? How do I use the observer to display a timeline of the current_user.changed_data?

Solution

API seems a little uncomfortable for now, anyway here's sample code that works in current merit master (1515c6463f92aaace6298015c0f8e70064885779):

class ReputationChangeObserver
  def update(changed_data)
    # description will be something like:
    #   granted 5 points
    #   granted just-registered badge
    #   removed autobiographer badge
    description = changed_data[:description]

    # If user is your meritable model, you can grab it like:
    if changed_data[:merit_object]
      sash_id = changed_data[:merit_object].sash_id
      user = User.where(sash_id: sash_id).first
    end

    # To know where and when it happened:
    merit_action = Merit::Action.find changed_data[:merit_action_id]
    controller = merit_action.target_model
    action = merit_action.action_method
    when = merit_action.created_at

    # From here on, you can create a new Notification assuming that's an
    # ActiveRecord Model in your app, send an email, etc. For example:
    Notification.create(
      user: user,
      what: description,
      where: "#{controller}##{action}",
      when: when)
  end
end

EDIT: Please note that API has changed since this answer, see https://github.com/tute/merit#getting-notifications.