/**
* Return a Jam_Query_Builder_Join object to allow a query to join with this association
* You can join polymorphic association only when you pass an alias, wich will be used as the
* name of the model to match to the polymorphic_key
*
* @param string $alias table name alias
* @param string $type join type (LEFT, NATURAL)
* @return Jam_Query_Builder_Join
*/
public function join($alias, $type = NULL)
{
if ($this->is_polymorphic()) {
$foreign_model = $alias;
if (!$foreign_model) {
throw new Kohana_Exception('Jam does not join automatically polymorphic belongsto associations!');
}
$join = new Jam_Query_Builder_Join($foreign_model, $type);
$join->on(DB::expr(':model', array(':model' => $foreign_model)), '=', $this->polymorphic);
} else {
$join = new Jam_Query_Builder_Join($alias ? array($this->foreign_model, $alias) : $this->foreign_model, $type);
}
return $join->context_model($this->model)->on(':primary_key', '=', $this->foreign_key);
}
