/**
* Set schema fields
*
* @param Schema $schema
*/
public static function fields($schema)
{
$schema->id();
$schema->string('title')->maxLength(128)->minLength(3)->required();
$schema->toOne(Author::class, 'author');
$schema->toOne(Isbn::class, 'isbn', 'isbn_code', 'code');
$schema->throughMany('orders', Order::class)->resolver(OrderBook::class, 'book', 'order');
// $schema -> throughMany('orders',Order::class,'id','id');
// $schema -> throughMany('orders',Order::class) -> inModel(OrderBook::class)
// $schema -> throughMany('orders',Order::class) -> inTable('orders_books')
// $this -> orders -> add(Order $order);
// $this -> orders // Collection orders
// $this -> orders -> get(0) -> pivot. OrderBoook
$schema->updated_at();
$schema->created_at();
}