How to preload associations of an association that is actually cached in the association_cache

preloading_subassociations.rb

# Using measurement.measured_questionnaires.preload(:questionnaire) would lead to reloading 
# both the measured_questionnaires and the questionnaires each time you call it,
# requiring a explicit memoization somewhere which could go out of sync.
# usage: measurement.measured_questionnaires.with_questionnaires.map { ... }
class Measurement < ActiveRecord::Base
  has_many :measured_questionnaires, -> { order(:position) } do
    def with_questionnaires
      ActiveRecord::Associations::Preloader.new.preload(self, :questionnaire)
      self
    end
  end