public function with($relationSelector)
{
$relations = ModelQueryBuilderHelper::extractRelations($this->_model, $relationSelector);
$field = '';
foreach ($relations as $relation) {
$nestedField = $field ? $field . '->' . $relation->getName() : $relation->getName();
$this->_addRelationToFetch(new RelationToFetch($field, $relation, $nestedField));
$field = $nestedField;
}
return $this;
}