einundzwanzig-portal/app/Nova/Category.php

<?php

namespace App\Nova;

use Illuminate\Http\Request;
use Laravel\Nova\Fields\BelongsToMany;
use Laravel\Nova\Fields\ID;
use Laravel\Nova\Fields\Text;

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

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

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

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

            Text::make(__('Name'), 'name')
                ->rules('required', 'string'),

            Text::make(__('Slug'), 'slug')
                ->rules('required', 'string', 'unique:categories,slug'),

            BelongsToMany::make(__('Courses'), 'courses', Course::class),

        ];
    }

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

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

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

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