course-site/app/Repositories/Models/Exam/PaperResult.php

<?php

namespace App\Repositories\Models\Exam;

use App\Repositories\Models\Base\Admin;
use App\Repositories\Models\Model;
use Prettus\Repository\Contracts\Transformable;
use Prettus\Repository\Traits\TransformableTrait;

/**
 * Class PaperResult.
 *
 * @package namespace App\Repositories\Models\Exam;
 */
class PaperResult extends Model implements Transformable
{
    use TransformableTrait;

    protected $table = 'exam_paper_results';
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $guarded = [];

    protected $casts = [
        'result' => 'array',
        'imgs' => 'array'
    ];

    public function paper()
    {
        return $this->belongsTo(Paper::class)->select(['id', 'name', 'submit_nums', 'topic_nums', 'mark']);
    }

    public function assign_admin()
    {
        return $this->belongsTo(Admin::class)->select(['id', 'username', 'name']);
    }

    public function polling_admin()
    {
        return $this->belongsTo(Admin::class)->select(['id', 'username', 'name']);
    }

    public function getImgUrlsAttribute()
    {
        $imgs = $this->fromJson($this->attributes['imgs']);
        $urls = [];
        if (is_array($imgs)) {
            foreach ($imgs as $img) {
                $urls[] = path_to_url($img);
            }
        }
        return $urls;
    }

}