Defining Laravel foreign keys with Model Factories, One to One & One to Many Relationships without creating unnecessary models

So here is my solution:

The example deals with:

• Users & Profiles (for illustrating One to One relationships)

• Users & Posts (for illustrating One to Many relationships)

  // ONE TO ONE relationship (with Users already created)
  $factory->define(App\Profile::class, function (Faker\Generator $faker) {
      return [
          'user_id' => $faker->unique()->numberBetween(1, App\User::count()),
          // Rest of attributes...
      ];
  });
  
  // ONE TO MANY relationship (with Users already created)
  $factory->define(App\Posts::class, function (Faker\Generator $faker) {
      $users = App\User::pluck('id')->toArray();
      return [
          'user_id' => $faker->randomElement($users),
          // Rest of attributes...
      ];
  });
  

Here is a solution to make relationships that is way better than assigning random Users, especially if you need to send extra information to this model.

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    $user = factory('App\Models\User')->create(['email' => '[email protected]',]);
    // do your relationships here (...)
    return [
        'user_id' => $user->id,
        'title'   => $faker->sentence,
        'body'    => $faker->paragraph,
        ];
    }

And I saw another example with the use of anonymous function

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    return [
        'user_id' => function () {
            return factory(App\User::class)->create()->id;
        },
        'title' => $faker->sentence,
        'body'  => $faker->paragraph,
    ];
}

Source: https://laracasts.com/series/laravel-from-scratch-2017/episodes/22