instance_variables.each do |vn|
  v = instance_variable_get(vn)
  if v.class==WillPaginate::Collection
    json.iTotalRecords v.count
    json.iTotalDisplayRecords v.total_entries
  end
end
json.sEcho params["sEcho"].to_i
json.aaData do
  json.ingest! yield
end