empty json array is returned when the row doesn't exists in DB

Question

my function receives a http request and sends back json string as http response. This is my Code:

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)
}

Im getting the desired output when the input values are correct and the corresponding row exists in Db. but when the input is wrong or the query fails, i should return only the status as "failed" but my output contains the result [] which is empty like this.

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

I tried checking Result == nil and add the array only on true. but this doesn't help me. it might be because the struct is not nill. I need some help to to find the issue and solve it.

Umair Mohammad · Accepted Answer · 2018-03-07 09:22:14Z

2

Trying checking the length of the Result array before appending it to output

Something like this

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

Maybe you also need to write this also Result := make(map[string]interface{}) inside the if condition, before the append statement

answered Mar 7, 2018 at 9:22

Umair Mohammad

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3 Comments

Umair Mohammad Over a year ago

You can accept this as solution/upvote stackoverflow.com/help/someone-answers

siri Over a year ago

Result := make(map[string]interface{}) i cant use this in the condition because the output struct is local to the above block, and it should be inside it , if not the value gets initiated and when i send another request to the same function and the query fails, it shows the previous output @Umair

Umair Mohammad Over a year ago

Ok then try only putting append statement in if condition and without altering initialization statement

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