5min illustration of cheap and dirty change tracking with activerecord

change tracking.rb

# WARN: this relies on the single threaded nature of our apps!

class ApplicationModel < ActiveRecord::Base
  before_save do
    if ChangeTracking.currently_change_tracking?
      changeset << [:update, self, changes]
    end
  end

  before_create do
    if ChangeTracking.currently_change_tracking?
      changeset << [:create, self, changes]
    end
  end

  before_destroy do
    ...
  end
  
  # ... any other hooks/overrides to catch db changes, like .update_all()
end


class Loan < ApplicationModel
end

class AllOtherModelsInAppEtc... < ApplicationModel
end

module ChangeTracking
  attr_reader :current_change_tracking_session

  def with_dry_run
    # thread safety no-no but ok in our world
    self.current_change_tracking_session = {}

    ActiveRecord::Base.transaction do
      yield
      raise ActiveRecord::Rollback
    end

    current_change_tracking_session
  ensure
    self.current_change_tracking_session = nil
  end

  def currently_change_tracking?
    current_change_tracking_session.present?
  end
end


# Usage:
changes = ChangeTracking.with_dry_run do
  # call commands
  # do stuff
  # do more stuff
  # whatever
end

puts "the following changed:"
ap changes