Product.php

<?php

namespace App\Nova;

use App\Models\Retailer;
use App\Rules\isSKUAvailable;
use Illuminate\Http\Request;
use Laravel\Nova\Fields\ID;
use Laravel\Nova\Fields\Select;
use Laravel\Nova\Fields\Text;
use Laravel\Nova\Fields\Textarea;
use Laravel\Nova\Http\Requests\NovaRequest;

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

    /**
     * The single value that should be used to represent the resource when being displayed.
     *
     * @var string
     */
    public static $title = 'id';

    /**
     * The columns that should be searched.
     *
     * @var array
     */
    public static $search = [
        'id',
    ];

    public function getAllRetailers()
    {
        $list = array();
        foreach (Retailer::get() as $retailer) {
            $list[$retailer['id']] = $retailer['name'];
        }
        return $list;
    }

    /**
     * Get the fields displayed by the resource.
     *
     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
     * @return array
     */
    public function fields(NovaRequest $request)
    {
        return [
            ID::make()->sortable(),

            Text::make('Name')
                ->sortable()
                ->rules('required', 'max:255', 'min:2'),

            Select::make('Retailer', 'retailer_id')
                ->options(
                    $this->getAllRetailers()
                )
                ->rules('required'),

            Text::make('SKU')
                ->sortable()
                ->rules('required', new isSKUAvailable($request->retailer_id)),

            Text::make('Price')
                ->sortable()
                ->rules('required'),

            Textarea::make('Description')
                ->sortable()
                ->rules('required'),
        ];
    }

    /**
     * Get the cards available for the request.
     *
     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
     * @return array
     */
    public function cards(NovaRequest $request)
    {
        return [];
    }

    /**
     * Get the filters available for the resource.
     *
     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
     * @return array
     */
    public function filters(NovaRequest $request)
    {
        return [];
    }

    /**
     * Get the lenses available for the resource.
     *
     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
     * @return array
     */
    public function lenses(NovaRequest $request)
    {
        return [];
    }

    /**
     * Get the actions available for the resource.
     *
     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
     * @return array
     */
    public function actions(NovaRequest $request)
    {
        return [];
    }
}