Laravel Many-to-Many: Seed Data with Factories - 3 Ways

When you have a belongsToMany relationship, it's tricky to add the records in your Seeders/Factories. In this tutorial, I will show you three ways.

Setup: Model Factories

For this example, we will have three things:

• User model
• Task model
• Many-to-Many between them

app/Models/User.php

public function tasks(): BelongsToMany
{
    return $this->belongsToMany(Task::class);
}

First, we will need a User factory and a Task factory, without any relationships for now.

User Factory

public function definition(): array
{
    return [
        'name' => fake()->name(),
        'email' => fake()->unique()->safeEmail(),
        'email_verified_at' => now(),
        'password' => '$2y$10$92IXUNpkjO0rOQ5byMi.Ye4oKoEa3Ro9llC/.og/at2.uheWG/igi', // password
        'remember_token' => Str::random(10),
    ];
}

Task Factory

public function definition()
{
    return [
        'name' => fake()->name(),
    ];
}

Now, how to seed Users and assign a Task to each user?

I will show you three options, from the worst to the best one, in my opinion.

Option 1: afterCreating()

You can modify the User Factory and create Tasks every time after the User is created:

User Factory

// ...
public function configure()
{
    return $this->afterCreating(function (User $user) {
        // Will create 3 tasks for each new user
        Task::factory()->count(3)->create([
            'user_id' => $user->id,
        ]);
    });
}

And then, tasks will be created automatically when simply creating a user:

User::factory()->create();

But the problem is that it will always create tasks. You will not be able to create a user without tasks. This is not ideal.

Option 2: create()->each()

The second way is to edit Seeders: call ->each() after creating User and create tasks manually:

User Seeder

$users = User::factory()
    ->count(10)
    ->create()
    ->each(function(User $user) {
        Task::factory()
            ->count(3)
            ->create([
                'user_id' => $user->id,
            ]);
    });

This solves our problem of creating users without tasks. But the code still looks too long. There's a better way.

Option 3: has()

Once again, Laravel has a solution for us. We can use the has() method after calling Factories to tell them to create a relationship. Let's see how this works.

User Seeder

User::factory()
    // This tells the factory to create a relationship
    ->has(Task::factory())
    ->count(10)
    ->create();

As you can see, this is very simple, and it gives us the result we need:

If you need more tasks created per user, you can pass the number to the has() method:

User::factory()
    // Adding ->count(5) will create 5 tasks per user
    ->has(Task::factory()->count(5))
    ->count(10)
    ->create();

This will give us the following result of multiple tasks per user:

That's it! You can read more about this in the official documentation.