使用angular-ui-grid过滤空值的最佳方法是什么？

Question

我想为我的用户提供仅显示特定列的空值的行的功能。什么是最好的方法？ 我提出了这个解决方案，这对我来说很麻烦，重用过滤器输入文本字段：

"onRegisterApi" : function(gridApi){
  $scope.gridApi = gridApi;
  $scope.gridApi.core.on.filterChanged( $scope, function() {
    var grid = this.grid;
    var term = grid.columns[7].filters[0].term; // the column I am interested in empty values
    if( term == '_' ) {
      $log.info("Setting filter to external mode");
      $scope.grid.useExternalFiltering = true;
      for(var i=0; i< grid.rows.length;i++){
        var row = grid.rows[i];
        if(row.entity.privileges==null || row.entity.privileges.trim().length==0){
          $scope.gridApi.core.clearRowInvisible(row);
        }
        else{
          $scope.gridApi.core.setRowInvisible(row);
        }
      }
    }else if($scope.grid.useExternalFiltering==true){
      $log.info("Resetting filter back to internal mode");
      $scope.grid.useExternalFiltering = false;
      for(var i=0; i< grid.rows.length;i++){
        $scope.gridApi.core.clearRowInvisible(grid.rows[i]);
      }
    }
  });
}