Eloquent hasOne seems to be updating wrong table - laravel

Question

I am getting an integrity constraint violation on an update to my users table when I am adding the current User to a Product. I am also using uuids instead of auto-incrementing so it adds another layer of complexity. I think I might be declaring the relationships wrong.
The error looks like it is trying to update the users table tryiSQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: users.uuid (SQL: update "users" set "uuid" = ?, "updated_at" = 2019-09-24 13:18:05 where "uuid" = 8ee98fac-11f7-5114-b9f1-772fe9732a49)
users table
uuid
User.php
public function products(){
return $this->hasMany('App\Product', 'user_uuid', 'uuid');
}
products table
uuid
user_uuid
Product.php
class Product extends Model
{
use SoftDeletes;
use uuidTrait;
protected $primaryKey = 'uuid';
public $incrementing = FALSE;
public function user(){
return $this->hasOne('App\User', 'uuid', 'user_uuid');
}
public static function boot(){
parent::boot();
static::creating(function(Product $instance){
$instance->user()->save(auth()->user());
});
}
}

Answer 1

You need the uuid of the current user
static::creating(function(Product $instance){
if(empty($instance->uuid)){
$instance->uuid = auth()->user()->user_uuid;
}
});
or you use the associate function
$product = new Product;
//...
$product->save();
$user = User::find(Auth::user()->id);
$user->associate($product);
$user->save();