einundzwanzig-portal/app/Nova/Course.php

<?php

namespace App\Nova;

use Illuminate\Http\Request;
use Laravel\Nova\Fields\BelongsTo;
use Laravel\Nova\Fields\BelongsToMany;
use Laravel\Nova\Fields\Field;
use Laravel\Nova\Fields\ID;
use Laravel\Nova\Fields\Text;
use Laravel\Nova\Http\Requests\NovaRequest;
use ZiffMedia\NovaSelectPlus\SelectPlus;

class Course extends Resource
{
    /**
     * The model the resource corresponds to.
     * @var string
     */
    public static $model = \App\Models\Course::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 static function relatableLecturers(NovaRequest $request, $query, Field $field)
    {
        if ($field instanceof BelongsTo) {
            $query->where('team_id', $request->user()->current_team_id);
        }

        return $query;
    }

    /**
     * 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')
                ->rules('required', 'string'),

            BelongsTo::make('Lecturer'),

            SelectPlus::make('Categories', 'categories', Category::class)
                      ->usingIndexLabel('name'),

            BelongsToMany::make('Categories')->onlyOnDetail(),

        ];
    }

    /**
     * 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 [];
    }
}