community-manage/app/Models/Topic.php

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2019/6/6
 * Time: 11:21
 */

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class Topic extends Model
{
    //
    protected $table = 'topic';
    protected $guarded = [];

    public function ct()
    {
        return $this->hasMany('App\Models\CategoryTopic','topic_id','id');
    }
}