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Laravel: Eloquent - One to Many Relationship

Carlos Costa

One-to-Many relationship is the most common relationship in Laravel. This relationship is used when a model has multiple instances of another model.

Let’s say we have a User model and a Post model. A User can have multiple Posts, but a Post can only have one User.

In this node we will create migrations, models, factories and test to demonstrate how to create a One to Many relation.

Let’s start by creating our files:

php artisan make:model Post -mf --pest

Migrations

Ok, let’s define migrations for our models:

//posts
Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->timestamps();

    $table->string('title');
    $table->text('body');

    $table->unsignedBigInteger('user_id');
    $table->foreign('user_id')->references('id')->on('posts')->onDelete('cascade');
});

Models

And the relations in our models:

//post
namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    use HasFactory;

    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

Factories

And factories for our models:

//post
class PostFactory extends Factory
{
    public function definition(): array
    {
        return [
            'title' => fake()->sentence(),
            'body' => fake()->paragraph(),
            'user_id' => User::factory(),
        ];
    }
}

Tests

To finally, let’s create a test to check if our relation is working:

use App\Models\Post;
use App\Models\User;
use Illuminate\Foundation\Testing\RefreshDatabase;

uses(RefreshDatabase::class);

test('Post relationship with User', function () {
    $user = User::factory()
        ->has(Post::factory()->count(3))
        ->create();

    $this->assertCount(3, $user->posts);

    foreach ($user->posts as $post) {
        $this->assertInstanceOf(Post::class, $post);
    }

    $firstPost = $user->posts->first();

    $this->assertEquals($firstPost->user->id, $user->id);
});

References