Laravel模型关系 一对一深入研究

一，主表book

  class Book extends Model
{
//
protected $fillable=['title','price','num'];


public function bookCard(){
return $this->hasOne(BookCard::class);
}
}

二，关联表bookcard

class BookCard extends Model
{
    //
    protected $fillable=['number'];

    public function book(){
        return $this->belongsTo(Book::class);
    }
}

三，主表和关联表如何写

$booklist=Book::find(1);
$res=$booklist->bookCard()->create([
   'number'=>str_random(16),
]);