如何正确使用go-pg做queryOne？

Question

我想使用只向对象返回一行的go-pg进行queryOne，而不是数组。

这是我的简单代码：

var reportMessage *ReportMessage
    _, err := db.Model((*ReportMessage)(nil)).QueryOne(&reportMessage, `
    SELECT 
        SUM(total_order) total_order,
        SUM(total_message) total_message,
        SUM(hsm_message) hsm_message ,
        SUM(outbound_message) outbound_message ,
        SUM(inbound_message) inbound_message ,
        SUM(total_order_amount) total_order_amount 
        FROM report_message rm WHERE seller_id =? and "date" between ? and ?;

    `, sellerID, dateStart, dateEnd)

    if err != nil {
        return nil, err
    }

    return reportMessage, nil

type ReportMessage struct {
    ID               string    `json:"id"`
    SellerID         string    `json:"seller_id"`
    TotalOrder       int       `json:"total_order"`
    Date             time.Time `json:"date"`
    HsmMessage       int       `json:"hsm_message"`
    TotalMessage     int       `json:"total_message"`
    OutboundMessage  int       `json:"outbound_message"`
    InboundMessage   int       `json:"inbound_message"`
    TotalOrderAmount float32   `json:"total_order_amount"`
}

我希望它只返回reportMessage，而不是数组。

这是我的错误：

json: cannot unmarshal number into Go value of type models.ReportMessage

如何只查询一行并将其返回给object而不是array？

Answer 1

您需要初始化模型的一个实例并传递一个指向该实例的指针，而不是传递一个指向模型的未初始化nil指针的指针。

reportMessage := new(ReportMessage)
_, err := db.Model((*ReportMessage)(nil)).QueryOne(reportMessage, `
SELECT 
    SUM(total_order) total_order,
    SUM(total_message) total_message,
    SUM(hsm_message) hsm_message ,
    SUM(outbound_message) outbound_message ,
    SUM(inbound_message) inbound_message ,
    SUM(total_order_amount) total_order_amount 
    FROM report_message rm WHERE seller_id =? and "date" between ? and ?;

`, sellerID, dateStart, dateEnd)

if err != nil {
    return nil, err
}

return reportMessage, nil