dqyitt2954 2018-02-24 20:20
浏览 101
已采纳

不可能的类型切换案例:不能有动态类型

Have following struct:

package dto

type CapacityResponse struct{
    Val int
    Err error
    TransactionID string
}

func (r *CapacityResponse) GetError() (error) {
    return r.Err
}

func (r *CapacityResponse) SetError(err error)  {
    r.Err = err
}

func (r *CapacityResponse) Read() interface{}  {
    return r.Val
}

func (r *CapacityResponse) GetTransactionId() string  {
    return r.TransactionID
}

It's interface:

package dto

type Responder interface {
    Read() (interface{})
    GetError() (error)
    SetError(error)
    GetTransactionId() (string)
}

And following logic:

func handler(w http.ResponseWriter, r *http.Request) {
    cr := request2CacheRequest(r)
    responseChan := make(chan dto.Responder)

    go func() {
        responder := processReq(cr)
        responseChan <- responder
    }()

    go func() {
        for r := range responseChan {
            if (r.GetTransactionId() == cr.TransactionID) {
                switch r.(type) {
                //case dto.KeysResponse:
                //case dto.GetResponse:
                //case dto.RemoveResponse:
                //case dto.SetResponse:
                case dto.CapacityResponse:
                    if i, ok := r.Read().(int); ok {
                        fmt.Fprintf(w, fmt.Sprintf("{'capasity': %d, 'err': %s}", i, r.GetError()))
                    }

                }
            }
        }
    }()
}

I am getting exception:

impossible type switch case: r (type dto.Responder) cannot have dynamic type dto.CapacityResponse (missing GetError method)

Could you, please, help me to understand what is wrong here?

  • 写回答

2条回答 默认 最新

  • duanjiao5723 2018-02-24 20:31
    关注

    The error message is saying that a dto.Responder value cannot contain a dto.CapacityResponse because dto.CapacityResponse is missing one of the dto.Responder methods (GetError).

    The pointer type implements the interface. Change the case to:

     case *dto.CapacityResponse:
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
查看更多回答(1条)

报告相同问题?

悬赏问题

  • ¥15 微信公众平台自制会员卡可以通过收款码收款码收款进行自动积分吗
  • ¥15 随身WiFi网络灯亮但是没有网络,如何解决?
  • ¥15 gdf格式的脑电数据如何处理matlab
  • ¥20 重新写的代码替换了之后运行hbuliderx就这样了
  • ¥100 监控抖音用户作品更新可以微信公众号提醒
  • ¥15 UE5 如何可以不渲染HDRIBackdrop背景
  • ¥70 2048小游戏毕设项目
  • ¥20 mysql架构,按照姓名分表
  • ¥15 MATLAB实现区间[a,b]上的Gauss-Legendre积分
  • ¥15 delphi webbrowser组件网页下拉菜单自动选择问题