Parent ID in HasMany

use App\Models\PostImage;
use MoonShine\UI\Fields\ID;
use MoonShine\UI\Fields\Image;
use MoonShine\Laravel\Fields\Relationships\BelongsTo;
use MoonShine\Laravel\Resources\ModelResource;
use MoonShine\Laravel\Traits\Resource\ResourceWithParent;
 
class PostImageResource extends ModelResource
{
    use ResourceWithParent;
 
    protected string $model = PostImage::class;
 
    // ...
 
    protected function getParentResourceClassName(): string
    {
        return PostResource::class;
    }
 
    protected function getParentRelationName(): string
    {
        return 'post';
    }
 
    protected function formFields(): iterable
    {
        return [
            ID::make(),
            BelongsTo::make('Post'),
            Image::make('Path')
                ->when(
                    $parentId = $this->getParentId(),
                    static fn(Image $image): string => $image->dir("post_images/$parentId")
                )
            ,
        ];
    }
 
    // ...
}