Why Laravel Can't Guess Your Factory Relationships

Source: Dev.to

The Issue

final class Client extends Model
{
    public function user(): BelongsTo
    {
        return $this->belongsTo(User::class);
    }

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

$owner      = UserFactory::new()->create(['name' => 'Owner']);
$distributor = UserFactory::new()->create(['name' => 'Distributor']);

$client = ClientFactory::new()
    ->for($owner)
    ->for($distributor)
    ->create();

Laravel sets user_id to the distributor’s ID and leaves distributor_id null. This happens because for($model) looks only at the model’s class, not at the variable name. Since both $owner and $distributor are User instances, Laravel picks the first User relationship it finds (user).

Explicitly Specifying the Relationship

Tell Laravel which relationship to use by passing the relationship name as the second argument:

$client = ClientFactory::new()
    ->for($owner, 'user')
    ->for($distributor, 'distributor')
    ->create();

Now both foreign keys are populated correctly.

Alternative: Setting Foreign Keys Directly

Sometimes it’s clearer to assign the keys yourself:

$client = ClientFactory::new()->create([
    'user_id'        => $owner->id,
    'distributor_id' => $distributor->id,
]);

This avoids a chain of for() calls and makes the intent explicit.

Design Considerations

Laravel works best when you follow its conventions:

• A single relationship to a model (e.g., Client → User) is straightforward.
• Adding a second relationship to the same model can be confusing. In some cases, introducing a dedicated model (e.g., Distributor) may better express the domain.
• Naming matters. If the business language uses “owner” and “distributor,” naming the relationships accordingly reduces mental overhead.

Client   → Customer
user     → owner

Clear, domain‑specific names lead to fewer surprises.

Real‑world Example

$address = AddressFactory::new()
    ->for($user)
    ->has(
        DirectionFactory::new()
            ->has(
                DirectionScheduleFactory::new()->count(10),
                'schedules'
            )
    )
    ->create();

In this case, the default for($user) works because there is only one User relationship on Address.

Takeaways

• for() selects the first relationship matching the model’s class.
• Use the second argument to specify the exact relationship when multiple exist.
• Alternatively, set foreign keys directly in the factory payload.
• Align your model and relationship names with the domain language to avoid confusion.
• When the domain diverges from Laravel’s conventions, explicitness beats magic.

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Thanks to Joel Clermont for the original video that inspired this post. His Laravel tips are always worth checking out.