//显示清单列表    public function getIndex($user_id = null)    {        //读取当前所有设备        $checklists = DB::table(‘check_lists‘)            ->leftJoin(‘users‘, ‘check_lists.user_id‘, ‘=‘, ‘users.id‘)            ->select(‘check_lists.*‘, ‘users.email as user_name‘)
            ->when(!!$user_id, function($q) use ($user_id){                return $q->where(‘user_id‘, $user_id);            })
            ->paginate(10);        return view(‘admin.checklists.index‘,compact(‘checklists‘));    }