Extract method

report.rb

############################# first version
def generate
    @volunteers.includes(
       [:user, { taggings: :tag }]
      ).find_each(batch_size: 1000) do |volunteer|
        csv << VolunteerPresenter.new(volunteer).to_csv
     end
 end

############################ second version not working
def generate
  prefetch_volunteers do |volunteer|
    csv << VolunteerPresenter.new(volunteer).to_csv
  end
end

private

def prefetch_volunteers
  @volunteers.includes(
   [:user, { taggings: :tag }]
  ).find_each(batch_size: 1000)
end