public function instance($model, $altClass = null, $fail = false)
	{
		// get current class/model
		if(is_null($altClass))
			$class = get_class();
		else
			$class = (string) $class;

		// get instance
		if(is_a($model, $class))
			return $model;
		elseif(is_int($model))
			return ($fail) ? $this->findOrFail($model) : $this->find($model);

		return null;
	}