I want to make a new attribute called categories for the categories of the product in Algolia, So I use toSearchableArray():

<?php

use Laravel\Scout\Searchable;

class Product extends Model
{
    use Searchable;
    //...

    public function categories(){
        return $this->belongsToMany(MyCategory::class);
    }

    /**
     * Get the indexable data array for the model.
     *
     * @return array
     */
    public function toSearchableArray()
    {
        $array = $this->toArray();
        
        $extraFields = [
            'categories' => $this->categories->pluck('name')->toArray(),
        ];
 
        return array_merge($array, $extraFields);
    }
}

When I reset migration and seed, I see that categories attribute contains empty array.

categories: [],

I also tested with tinker and worked:

App\Models\Product::find(1)->toSearchableArray();

/* returns
[
     "id" => 1,
     "name" => "Laptop1",
     "slug" => "laptop-1",
     "details" => "15inch, 1TB SSD,3GB RAM",
     "price" => 22367,
     "description" => "Lorem1 ipsum dolor sit amet, consectetur adipisicing elit. Ipsum temporibus iusto ipsa, asperiores voluptas unde aspernatur praesentium in? Aliquam, dolore!",
     "created_at" => "2022-02-11T07:06:57.000000Z",
     "updated_at" => "2022-02-11T07:06:57.000000Z",
     "featured" => 0,
     "image" => null,
     "categories" => [
       "Laptops",
       "Desktops",
     ],
   ]
*/

Why categories contains empty array in Algolia and how can I fix It?

Thanks