Simple drag/drop reordering of records in an ActiveAdmin view table

activeadmin_sortable.js.coffee

# http://stackoverflow.com/a/8936202
#
# ActiveAdmin already includes the necessary jquery in active_admin/base,
# so just add this to javascripts/active_admin.js after //= require active_admin/base
# 
# 
# Serialize and Sort 
# 
# model_name - you guessed it, the name of the model we are calling sort on.
#              This is the actual variable name, no need to change it.
#
sendSortRequestOfModel = (model_name) ->
  formData = $('#' + model_name + ' tbody').sortable('serialize')
  formData += '&' + $('meta[name=csrf-param]').attr('content') + 
    '=' + encodeURIComponent($('meta[name=csrf-token]').attr('content'))
  $.ajax
    type: 'post'
    data: formData
    dataType: 'script'
    url: '/admin/' + model_name + '/sort'

# Don't forget we are sorting Duck, so ducks refers specifically to that.
#
jQuery ($) ->
  if $('body.admin_ducks.index').length
    $( '#ducks tbody' ).disableSelection()
    $( '#ducks tbody' ).sortable
      axis: 'y'
      cursor: 'move'
      update: (event, ui) ->
        sendSortRequestOfModel('ducks')

duck.rb

# admin/duck.rb
# Duck is the Model this particular file refers to. 
# Ref. ActiveAdmin documentation for more. 
# http://activeadmin.info/

ActiveAdmin.register Duck do
  config.sort_order = 'position_asc'

  ...

  collection_action :sort, :method => :post do
    params[:story].each_with_index do |id, index|
      Duck.update_all(['position=?', index+1], ['id=?', id])
    end
    render :nothing => true
  end
end

works like a charm - thnx!

You are the man. Great solution.

In case someone else encounters this and considers implementing this for has_many - this is already done:
activeadmin/activeadmin#2656 (comment)