screen/application/common/model/SiteMsg.php

<?php

namespace app\common\model;

use think\db\Query;
use think\Model;

/**
 * @method static Query|static hot($hot=1)
 */
class SiteMsg extends Model
{
    protected $autoWriteTimestamp=true;
    protected $updateTime=null;
    public function read(){
        return $this->hasMany(SiteMsgRead::class);
    }
    protected static function init()
    {
        self::afterDelete(function (self $msg){
            $msg->read()->delete();
        });
    }
}