# app/models/question.rb
def new_position=(position)
  insert_at(position.to_i)
end

# Make sure to add :new_position to permitted params in questions controller

# coffeescript
$(document).on 'turbolinks:load', ->
  $('.sortable').sortable
    axis: 'y'
    handle: '.handle'
    update: (e, ui) ->
      data = new FormData
      data.append "question[new_position]", ui.item.index() + 1
      Rails.ajax
        url: "/questions/#{ui.item.data('question-id')}"
        type: "PATCH"
        data: data