指定一个值以创建随机元素

Question

I'm trying to seed my database with faker, but I have some issues with a foreign element. I have one and only user and I don't know its id. I want all the posts to have its id.
This is how I did this :

public function run()
{
    factory(App\User::class)->create();
    factory(App\Category::class, 3)->create();

    $user = \App\User::first();

    factory(App\Post::class, 10)->create(['author_id' => $user->id]);
}

And this is my post factory :

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    return [
        'title' => $faker->unique()->sentence(5),
        'subtitle' => $faker->optional()->sentence(10),
        'markdown' => $faker->text(500),
        'draft' => $faker->boolean(),
        'category_id' => $faker->numberBetween(1, 6),
    ];
});

After a db:seed, this is the error I get (users and categories are well populated) :

  SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`laman`.`posts`, CO
  NSTRAINT `posts_author_id_foreign` FOREIGN KEY (`author_id`) REFERENCES `users` (`id`)) (SQL: insert into `posts` (`title`, `slug`, `subtit
  le`, `markdown`, `draft`, `category_id`, `author_id`, `html`, `published_at`, `updated_at`, `created_at`) values (title.,
   slug, , markdown, 0, 6, 1, html, 2017-04-25 20:08:34, 2017-04-25 20:08:34, 2017-04-25
  20:08:34))

Here the user id is 1 or it should be 9. Why?

Answer 1

i recommend to seed your DB as follows:

1. To avoid manually deleting db entries, populate your seeder with DB::table('YourDBTable')->truncate(); :

   public function run()
   {
       DB::table('user')->truncate();
       DB::table('posts')->truncate();
   
       factory(App\User::class)->create();
       factory(App\Category::class, 3)->create(); 
   
       $user = \App\User::first();
   
       factory(App\Post::class, 10)->create(['author_id' => $user->id]);
   }
   

Now everytime you run artisan command db:seed, you truncate your users table after which you are populating your db with fresh data and thus you are able to fetch the single one user, and the right one too, with the first() method.