public function handle()
   {
       //通知每个用户系统消息
     $users = \App\User::all();
     foreach($users as $user){
        $user->addNotice($this->notice);
     }
   }
}

public function store(){
   $this->validate(request(),[
       'title' => 'required|string',
       'content' => 'required|string',
   ]);

   $notice = \App\Notice::create(request(['title','content']));

   dispatch(new \App\Jobs\SendMessage($notice));

   return redirect('/admin/notices');

}

//用户收到的通知
public function notices(){
   return $this->belongsToMany(\App\Notice::class,'user_notice','user_id','notice_id')->withPivot(['user_id','notice_id']);
}

//给用户增加通知
public function addNotice($notice){
   return $this->notices()->save($notice);
}

添加一条通知后，没报错,user_notice表中没有数据，老师这是为什么