https://github.com/pokonski/public_activity の拡張。modelでインクルードして使うととりあえずトラックしまくる。消すのは忍びないので置いておく。

public_activity_tracker.rb

# 使用したいモデルでインクルード
# ex) include Concerns::ActivityTracker
module Concerns::PublicActivityTracker
  extend ActiveSupport::Concern

  module ClassMethods

    # create, update, destroy を監視します。
    # 引数に only か except を渡すことで update を監視したいカラムを限定できます。
    #
    # ex) track_enable
    # ex) track_enable only: [:name, :updated_at]
    # ex) track_enable except: [:name, :updated_at]
    def track_enable(options = Hash.new)
      if options.present?
        if !options.instance_of?(Hash)
          raise 'Invalid options'
        elsif options.keys.reject{|k| [:only, :except].include? k}.present?
          raise 'Invalid options'
        else
          [:only, :except].each do |key|
            option = options[key].presence
            if option.present?
              if option.instance_of?(String) || option.instance_of?(Symbol)
                options[key] = [option.to_s]
              elsif !option.instance_of?(Hash)
                raise 'Invalid options'
              end
            end
          end
        end
      end

      attrs = self.attribute_names - ['id']
      if options[:only].present?
        attrs &= options[:only]
      elsif options[:except].present?
        attrs -= options[:except]
      end

      define_method :tracking_activity_on_update do
        attrs.each do |a|
          if self.instance_eval("#{a}_changed?")
            self.create_activity :update, get_controller_options
            break
          end
        end
      end
      private :tracking_activity_on_update

      self.send('after_create', :'tracking_activity_on_create')
      self.send('after_update', :'tracking_activity_on_update')
      self.send('before_destroy', :'tracking_activity_on_destroy')
    end

  end

  private

  def tracking_activity_on_create
    self.create_activity :create, get_controller_options
  end

  def tracking_activity_on_destroy
    self.create_activity :destroy, get_controller_options
  end

  def get_controller_options
    controller = PublicActivity.get_controller
    controller.present? ? { owner: controller.current_user, params: controller.params } : nil
  end

end