Laravel，调用未定义函数 Database\Seeders\factory()

I get the title error when I run command:

php artisan db:seed

My screenshot:

I have no idea where this problem comes from. I was searching for code examples and solution but I haven't found anything :(

ArticlesTableSeeder.php

<?php

namespace Database\Seeders;

use Illuminate\Database\Seeder;
// use Laracasts\TestDummy\Factory as TestDummy;

class ArticlesTableSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
        factory(App\Models\Article::class, 30)->create();
    }
}

ArticleFactory.php

<?php

namespace Database\Factories;

use App\Models\Model;
use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;

class ModelFactory extends Factory
{
    /**
     * The name of the factory's corresponding model.
     *
     * @var string
     */
    protected $model = App\Models\Article::class;

    /**
     * Define the model's default state.
     *
     * @return array
     */
    public function definition()
    {
        return [
            'title' => $faker->text(50),
            'body' => $faker->text(200)
        ];
    }
}

数据库 seeder 机.php

<?php

namespace Database\Seeders;

use Illuminate\Database\Seeder;

class DatabaseSeeder extends Seeder
{
    /**
     * Seed the application's database.
     *
     * @return void
     */
    public function run()
    {
        $this->call(ArticlesTableSeeder::class);
    }
}

提前感谢您的帮助！