gistfile1.txt

Tested on: Datatable 1.8.2, Rails 3.1.3
This example uses Coffeescript and Haml (you should too :-) )

The following is an example of Datatables server-side processing of a table 
which displays a user's song list including the songs' artist names.  In 
Rails, Song and Artist are ActiveRecord models in a one artist-many song relat.

1a. the Rails controller code

class SongsController < ApplicationController
  ...
  def datatable_my_songs
    @songs = current_user.songlist.songs
    data = Hash.new
    #pagination - see doc
    #data["sEcho"] = see doc
    #data["iTotalRecords"] = see doc
    #data["iTotalDisplayRecords"] = see doc
    data["aaData"] = @songs.as_json :include=>{:artist=>{:only=>:name}}
    render :json=>data.to_json
  end

Notes:
- if no "aaData" prop will get error described here https://gist.github.com/1661626
- need :include to load related obj data, more here: https://gist.github.com/1542498


1a. Add a Rails Route
  Something like:

  match "my_songs" => "songs#datatable_my_songs"

2.  Client Side

##assets/javascripts/songs.js.coffee
initSongTable = ->
  $("#mySongsTable").dataTable
    "bPaginate": false,
    "bServerSide": true,
    "sAjaxSource": "/my_songs",  #should be the named rails route
    "aoColumns": [
          { "mDataProp": "song.name" },
          { "mDataProp": "song.artist.name" },
          { "mDataProp": null}
          ]
    "fnServerData":  ( sSource, aoData, fnCallback ) ->
      $.getJSON sSource, aoData, (json) ->
          #Do whatever additional processing you want on the callback
          #then tell DataTables
          fnCallback(json)
    "fnRowCallback": (nRow, aData, iDisplayIndex) ->
          obj = aData.song
          $('td:eq(2)', nRow).html objLinksTmpl("song", obj)
          nRow


3.  Html Page

Make sure you have same num of %th elems as aoColumns (each of which needs mDataProp - which can be null - or get popup warning here https://gist.github.com/1660712)

I use a partial, though you can write a table directly.  Remember to call your table init function.  I use a helper method js(jsFunctionName) as detailed below.

##songs/index.html.haml
= render :partial=>"shared/dataTable", :locals =>{:tableId=>"mySongsTable", :columns=>["Name", "Artist","Actions"]}
js "initSongTable"


##shared/_dataTable.rb
%table{:id=>tableId}
  %thead
    %tr
      - columns.each do |col|
        %th #{col}
  %tbody


##helpers/html_helper.rb
module HtmlHelper

  def js(function)
    function += (!function.end_with?("()") ? "()" : "" )
    fn = <<-STR
      <script>
        $(function(){
          var root = window || global;
          root.#{function};
        });
      </script>
    STR
    fn.html_safe
  end