Can`t order by nested objects

[leonardoResendeLima]

I have and object that has nested properties inside, like this:

{
   ...
   file :  {
      type : "Excel",
      size : 10000
   }
}

and I can`t filter the "type" field.

<table class="table table-bordered table-condensed table-hover center">
   <thead>
      <tr>
         <th sortable="file.type" class="sortable">
            {{'Actions.Tabela.FileType' | translate}}
         </th>
      </tr>
      <tr>
         <td>
            <input type="text" class="form-control input-sm order-search-box" ng-change="gridActions.filter()" ng-model="file.type" filter-by="file.type" filter-type="text">
         </td>
      </tr>
      <tr>
         <td ng-bind="file.type"></td>
      </tr>
</table>