Laravel Resource toArray get seq

1、背景：需要根据接口中文章的位置计算曝光，曝光由文章首图的日志统计处理，所以需要在文章首图的url中拼上当前文章的在此次接口中的位置以及当前页码

2、实现：当前文章在此次接口返回数据中的位置；

use Illuminate\Http\Resources\Json\Resource;
use App\Models\Traits\WithIndexTrait;

class SubjectToArrayResource extends Resource
{
    use WithIndexTrait;

    public $resource;

    // default constructor to make
    // anonymous class work
    public function __construct($resource = null)
    {
        if ($resource) {
            parent::__construct($resource);
        }
    }

    public function toArray($request)
    {
        ……
        $this->index
        ……
    }

    public function with($request)
    {
        return [
            'errcode' => 0,
            'msg'     => 'ok'
        ];
    }
}

use App\Ship\Http\Json\ApiCollection;

trait WithIndexTrait
{
    public $index;

    public static function collection($resource)
    {
        return new class($resource, get_called_class()) extends ApiCollection
        {
            /**
             * @var string
             */
            public $collects;

            /**
             * Create a new anonymous resource collection.
             *
             * @param mixed $resource
             * @param string $collects
             */
            public function __construct($resource, $collects)
            {
                $this->collects = $collects;

                parent::__construct($resource);
            }

            public function toArray($request)
            {
                return $this->collection
                    ->map(function ($item, $key) use ($request) {
                        // 这个item指的是resource,不是model
                        $item->index = $key;
                        return $item->toArray($request);
                    })
                    ->all();
            }
        };
    }
}