Multiple tables in Orchid resource

[LemonPie22]

I have a main products table:

        Schema::create('products', function (Blueprint $table) {
            $table->id();
            $table->string('code', 255)->unique();
            $table->string('name');
            $table->string('description');
            $table->foreignId('product_type_id')->index();
            $table->timestamps();
            $table->softDeletes();
            $table->foreign('product_type_id')->references('id')->on('product_types');
        });

And an additional table for each product type. For example, belts:

        Schema::create('belts', function (Blueprint $table) {
            $table->id();
            $table->foreignId('product_id')->index();
            $table->string('dimensions');
            $table->timestamps();
            $table->softDeletes();
            $table->foreign('product_id')->references('id')->on('products');
        });

The reason for this approach is that I want to make sure each product has a unique code. I'm aware that I could achieve this with a single table but then I would have to make mandatory columns (such as the dimensions column) nullable. Plus I would have to amend the table schema each time a new product type is added.

I have set up the Product model as follows:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Orchid\Attachment\Attachable;
use Orchid\Filters\Filterable;
use Orchid\Screen\AsSource;

class Product extends Model
{
    use AsSource, Filterable, Attachable, HasFactory;

    /**
     * @var array
     */
    protected $fillable = [
        'code',
        'name',
        'description',
        'product_type_id'
    ];

    /**
     * Get the belt this product owns.
     */
    public function belt()
    {
        return $this->hasOne(Belt::class);
    }
}

And the Belt model as follows:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Orchid\Attachment\Attachable;
use Orchid\Filters\Filterable;
use Orchid\Screen\AsSource;

class Belt extends Model
{
    use AsSource, Filterable, Attachable, HasFactory;
    
    /**
     * @var array
     */
    protected $fillable = [
        'product_id',
        'dimensions'
    ];

    /**
     * Get the product that owns this belt.
     */
    public function product()
    {
        return $this->belongsTo(Product::class);
    }
}

I have created an Orchid belt resource as follows:

<?php

namespace App\Orchid\Resources;

use Orchid\Crud\Resource;
use Orchid\Screen\TD;
use Orchid\Screen\Fields\Input;

use App\Orchid\Resources\UserResource;
use Illuminate\Support\ServiceProvider;
use Orchid\Crud\Arbitrator;

class BeltResource extends Resource
{
    /**
     * The model the resource corresponds to.
     *
     * @var string
     */
    public static $model = \App\Models\Belt::class;

    /**
     * Get the fields displayed by the resource.
     *
     * @return array
     */
    public function fields(): array
    {
        return [
            Input::make('product_type')
            ->hidden()
            ->value('1'),
            Input::make('code')
            ->title('Code')
            ->placeholder('Enter unique product code here'),
            Input::make('name')
            ->title('Name')
            ->placeholder('Enter belt name here'),     
            Input::make('description')
            ->title('Description')
            ->placeholder('Enter belt description here'),
            Input::make('dimensions')
            ->title('Dimensions')
            ->placeholder('Enter belt dimensions here'),     
        ];
    }

    /**
     * Get the columns displayed by the resource.
     *
     * @return TD[]
     */
    public function columns(): array
    {
        return [
            TD::make('code'),
            TD::make('name'),
            TD::make('dimensions'),

            TD::make('created_at', 'Date of creation')
                ->render(function ($model) {
                    return $model->created_at->toDateTimeString();
                }),

            TD::make('updated_at', 'Update date')
                ->render(function ($model) {
                    return $model->updated_at->toDateTimeString();
                }),
        ];
    }

    /**
     * Get the sights displayed by the resource.
     *
     * @return Sight[]
     */
    public function legend(): array
    {
        return [];
    }

    /**
     * Get the filters available for the resource.
     *
     * @return array
     */
    public function filters(): array
    {
        return [];
    }
}

This gives me the following new belt form:

When I try to create a belt I get the following error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'product_type' in 'field list'

insert into `belts` (`product_type`, `code`, `name`, `description`, `dimensions`, `updated_at`, `created_at`) values (1, belt0001, Belt #1, Belt number 1, 3.15 by 26.22, 2022-06-14 15:14:23, 2022-06-14 15:14:23)

I can see why this error is occurring but I'm not sure how best to address it.

I'd be grateful for any pointers.

[LemonPie22]

Answering (kind of) this myself in case others have the same question.

What I was trying to achieve is Multi-Table Inheritance (MTI). After researching the topic I realised I would be better off using Single-Table Inheritance (STI) instead. That was much easier to achieve and resulted in a simpler database schema.