laravel 工厂和多态关系

Question

我有一个播种机可以做到这一点，

public function run()
    {
        factory(App\User::class, 20)->create()->each(function($user){
            if($user->type == "performer") {
                $user->listings()->saveMany(factory(App\Listing::class, rand(1, 10)))->create([
                    'user_id' => $user->id
                ])->each(function($listing){
                    $listing->assets()->save(factory(App\Asset::class))->make([
                        'assetable_type' => 'App\Listing',
                        'assetable_id' => $listing->id,
                        'user_id' => $listing->user_id
                    ]);
                });
            }
        });
    }

此用户以下工厂，

    <?php

    /** @var \Illuminate\Database\Eloquent\Factory $factory */

    use App\Asset;
    use Faker\Generator as Faker;

    $factory->define(Asset::class, function (Faker $faker) {
        return [
            'type' => 'image',
            'url' => $faker->imageUrl(666, 461, 'cats'),
            'is_primary' => $faker->randomElements([true, false])
        ];
    });

    <?php

    /** @var \Illuminate\Database\Eloquent\Factory $factory */

    use App\Listing;
    use Faker\Generator as Faker;

    $factory->define(Listing::class, function (Faker $faker) {
        return [
            'name' => $faker->sentence(20, true),
            'slug' => $faker->slug(),
            'description' => $faker->realText(420),
            'booking_details' => $faker->realText(120),
            'cost' => $faker->randomFloat(2, 10, 250)
        ];
    });

    <?php

    /** @var \Illuminate\Database\Eloquent\Factory $factory */

    use App\User;
    use Faker\Generator as Faker;
    use Illuminate\Support\Str;

    /*
    |--------------------------------------------------------------------------
    | Model Factories
    |--------------------------------------------------------------------------
    |
    | This directory should contain each of the model factory definitions for
    | your application. Factories provide a convenient way to generate new
    | model instances for testing / seeding your application's database.
    |
    */

    $factory->define(User::class, function (Faker $faker) {
        return [
            'name' => $faker->name,
            'slug' => $faker->slug,
            'email' => $faker->unique()->safeEmail,
            'email_verified_at' => now(),
            'password' => '$2y$10$92IXUNpkjO0rOQ5byMi.Ye4oKoEa3Ro9llC/.og/at2.uheWG/igi', // password
            'remember_token' => Str::random(10),
            'type' => $faker->randomElement(['user', 'performer', 'admin'])
        ];
    });

一个用户可以有很多列表（1:n），一个列表可以有很多资产（这是多态的，因为其他模型也可以有模型）

首先，当我运行播种机时，出现以下错误，

传递给 Illuminate\Database\Eloquent\Relations\HasOneOrMany::save() 的参数 1 必须是 Illuminate\Database\Eloquent\Model 的实例，给定的 Illuminate\Database\Eloquent\FactoryBuilder 的实例

这是抛出$listings->assets()->save()

其次，我似乎在我的 UsersSeeder （用户、列表和资产）中生成了很多内容，这是可以的，因为没有用户你不能拥有列表，同样在我的代码中你不能没有没有资产上市？ 有没有更好的方法来播种这些数据和关系？