arrays - 当数据库中不存在该行时，返回空的 json 数组

Question

我的函数接收到一个 http 请求并发回 json 字符串作为 http 响应。这是我的代码:

func homePage(res http.ResponseWriter, req *http.Request) {
    type Resp struct {
        Result []map[string]interface{} `json:"result,omitempty"`
        Status string                   `json:"status"`
    }
    type Inputs struct {
        ShopID   string `json:"ShopID"`
        DeviceID string `json:"DeviceID"`
        EmpID    string `json:"EmpID"`
        Token    string `json:"Token"`
        Version  string `json:"Version"`
    }

    var Response Resp
    Response.Status = "failed"

    db, err := sql.Open("mysql", "root:password@tcp(127.0.0.1:3306)/b2b")

    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    rnd := render.New()
    b, err := ioutil.ReadAll(req.Body)
    defer req.Body.Close()

    if err != nil {
        panic(err.Error())
    }
    // Unmarshal the request body
    var msg Inputs
    err = json.Unmarshal(b, &msg)
    if err != nil {
        panic(err.Error())
    }

    bookingrows, bookingerr := db.Query("SELECT DISTINCT b2b_booking_id,b2b_check_in_report,b2b_vehicle_at_garage,b2b_service_under_progress,b2b_vehicle_ready,b2b_vehicle_delivered FROM b2b_booking_tbl WHERE b2b_flag=0 and b2b_shop_id=?", msg.ShopID)
    if bookingerr != nil {
        panic(bookingerr.Error())
    } else {

        Result := make(map[string]interface{})
        for bookingrows.Next() {
            var bookingid, checkinreported, vehicleingarage, serviceinprogress, vehicleready, vehicledelivered string
            err = bookingrows.Scan(&bookingid, &checkinreported, &vehicleingarage, &serviceinprogress, &vehicleready, &vehicledelivered)
            type Output struct {
                checkins   int `json:"checkins"`
                inprogress int `json:"inprogress"`
                ready      int `json:"ready"`
                completed  int `json:"completed"`
            }
            var output Output
            if err != nil {
                panic(err.Error())
                Response.Status = "failed"
            }
            if vehicledelivered == "1" {
                output.completed = output.completed + 1
            }
            if vehicledelivered == "0" && vehicleready == "1" {
                output.ready = output.ready + 1
            }
            if vehicledelivered == "0" && vehicleready == "0" && serviceinprogress == "1" {
                output.inprogress = output.inprogress + 1
            }
            if vehicledelivered == "0" && vehicleready == "0" && serviceinprogress == "0" && (checkinreported == "1" || vehicleingarage == "1") {
                output.checkins = output.checkins + 1
            }

            values := make([]string, 4)
            val := reflect.ValueOf(output)
            for i := range values {
                //Result[usercolumns[i]] = fmt.Sprintf("%s", v)
                Result[val.Type().Field(i).Tag.Get("json")] = fmt.Sprintf("%v", i)
            }
        }

        Response.Result = append(Response.Result, Result)
        Response.Status = "success"

    }

    res.Header().Set("Content-Type", "application/json")
    rnd.JSON(res, http.StatusOK, Response)
}

当输入值正确并且 Db 中存在相应的行时，我将获得所需的输出。但是当输入错误或查询失败时，我应该只返回“失败”状态，但我的输出包含结果 []，它像这样是空的。

{
    "result": [
        {}
    ],
    "status": "success"
} 

我尝试检查 Result == nil 并仅在 true 时添加数组。但这对我没有帮助。可能是因为该结构不是空的。我需要一些帮助来找到问题并解决它。

Answer 1

在将其附加到输出之前尝试检查 Result 数组的长度

像这样

if (len(Result) != 0) {
    Response.Result = append(Response.Result, Result)
}

也许您还需要在 if 条件中，在追加语句之前编写 Result := make(map[string]interface{})