How to get access to the entity from the form model?

Question

Yii

There is a Car(Active Record) class and there is a Bike(Active Record) class.
The Car class has a link to Bike hasmany.
Created a form (extends Model) to add new records to Car;
I pass the Car model to the form class and save it via save.
The question is, in the Car form class, I need to access to save data to Bike.
How can this be done?*

Answer 1

$bikes = $car->bikes;
foreach($bikes as $bike) {
  ...
}

Answer 2

The question is, in the Car form class, I need to access to save data to Bike.

Create a Bike model object, write data to it, link to the Car object