In Laravel 8, it's ridiculously simple and magical:

$numberOfProducts = 8;

return Category::factory()
    ->hasProducts($numberOfProducts)
    ->create();

There are quite a few more alternatives to create relationships. Pls check the docs for more.

I also suggest generate products this way:

class ProductFactory extends Factory
{
    public function definition()
    {
        return [
            'category_id' => function () {
                return Category::factory()->create()->id;
            }
        ];
    }
}

kevin, all that does is create 1 product , this is what worked for me instead

Product::factory() ->has(Category::factory())->count(10) ->create();

Great! Have you define the products relationship in the Category model:

class Category extends Model
{
    public function products()
    {
        return $this->hasMany(Product::class);
    }
}

yes i have , thanks :)