解决 GORM 一对一关联映射的疑问

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我在 gorm 映射方面遇到了一个奇怪的问题，我有两个如下所示的结构。

type parcelorder struct {
    gorm.model
    id                 int                `json:"id"`
    senderid           uint               `json:"sender_id"`
    orderid            string             `json:"order_id"`
    pickupaddress      string             `json:"pickup_address"`
    deliveryaddress    string             `json:"delivery_address"`
    createdat          time.time          `json:"created_at"`
    updatedat          time.time          `json:"updated_at"`
    deletedat          sql.nulltime       `json:"deleted_at"`
    parcelorderdetails parcelorderdetails `gorm:"foreignkey:parcelorderid"`
}
type parcelorderdetails struct {
    gorm.model
    id            int           `json:"id"`
    bikerid       sql.nullint32 `json:"biker_id"`
    parcelorderid int           `json:"parcel_order_id"`
    pickuptime    sql.nulltime  `json:"pickup_time"`
    deliverytime  sql.nulltime  `json:"delivery_time"`
    status        int           `json:"status"`
    createdat     time.time     `json:"created_at"`
    updatedat     time.time     `json:"updated_at"`
    deletedat     sql.nulltime  `json:"deleted_at"`
}

我正在使用 mysql 数据库，当我尝试创建订单时，它没有在第二个表上创建条目。 为了创建，我使用下面的代码

order := parcelorder{
        deliveryaddress: pickupdata.deliveryaddress,
        pickupaddress:   pickupdata.pickupaddress,
        orderid:         getuniqueid(),
        senderid:        userid,
        parcelorderdetails: parcelorderdetails{
            status: 0,
        },
    }
connection.create(&order)

此外，当我尝试从表中获取数据时，我收到如下错误

select `parcel_orders`.`id`,`parcel_orders`.`created_at`,`parcel_orders`.`updated_at`,`parcel_orders`.`deleted_at`,`parcel_orders`.`sender_id`,`parcel_orders`.`order_id`,`parcel_orders`.`pickup_address`,`parcel_orders`.`delivery_address`,`parcelorderdetails`.`id` as `parcelorderdetails__id`,`parcelorderdetails`.`created_at` as `parcelorderdetails__created_at`,`parcelorderdetails`.`updated_at` as `parcelorderdetails__updated_at`,`parcelorderdetails`.`deleted_at` as `parcelorderdetails__deleted_at`,`parcelorderdetails`.`biker_id` as `parcelorderdetails__biker_id`,`parcelorderdetails`.`parcel_order_id` as `parcelorderdetails__parcel_order_id`,`parcelorderdetails`.`pickup_time` as `parcelorderdetails__pickup_time`,`parcelorderdetails`.`delivery_time` as `parcelorderdetails__delivery_time`,`parcelorderdetails`.`status` as `parcelorderdetails__status` from `parcel_orders` parcelorder left join `parcel_order_details` `parcelorderdetails` on `parcel_orders`.`id` = `parcelorderdetails`.`parcel_order_id` where parcelorder.sender_id = 2

我的获取代码如下。获取问题非常奇怪，因为别名被指定为 parcelorder，因此未使用该名称标识的字段，而是仍然使用 parcel_orders 实际表名称

db.Joins("ParcelOrder").Joins("ParcelOrderDetails").Where("ParcelOrder.sender_id = ?", userId).Find(&order)

数据库不是用 go 应用程序创建的，而是用 laravel 应用程序创建的。我正在尝试向该数据库读取/写入数据。

有什么想法吗？

正确答案

答案很简单，但很难理解。

您只需添加更改：

parcelorderdetails parcelorderdetails `gorm:"foreignkey:parcelorderid"`

进入

parcelorderdetails *parcelorderdetails `gorm:"foreignkey:parcelorderid"`

原因是 parcelorderdetails 每次初始化 parcelorder 时都会创建一个空模型（非空），当然在某些情况下我们不打算意外创建 parcelorderorderdetails 因为它是一个空模型，我认为 gorm 会处理这种情况。

因此，如果你将其设置为 *parcelorderorderdetails，则默认情况下它将是 nil，这意味着 gorm 不会创建 parcelorderorderdetails，反之亦然。

这是我的完整代码

// https://stackoverflow.com/questions/69977516/unsupported-relations-for-schema-with-has-many-relation-in-gorm/70082006#70082006
package main

import (
    "database/sql"
    "fmt"
    "time"

    "gorm.io/driver/mysql"
    "gorm.io/gorm"
    "gorm.io/gorm/logger"
)

type parcelorder struct {
    gorm.model
    id                 int                `json:"id"`
    senderid           uint               `json:"sender_id"`
    orderid            string             `json:"order_id"`
    pickupaddress      string             `json:"pickup_address"`
    deliveryaddress    string             `json:"delivery_address"`
    createdat          time.time          `json:"created_at"`
    updatedat          time.time          `json:"updated_at"`
    deletedat          sql.nulltime       `json:"deleted_at"`
    parcelorderdetails *parcelorderdetails `gorm:"foreignkey:parcelorderid"`
}

type parcelorderdetails struct {
    gorm.model
    id            int           `json:"id"`
    bikerid       sql.nullint32 `json:"biker_id"`
    parcelorderid int           `json:"parcel_order_id"`
    pickuptime    sql.nulltime  `json:"pickup_time"`
    deliverytime  sql.nulltime  `json:"delivery_time"`
    status        int           `json:"status"`
    createdat     time.time     `json:"created_at"`
    updatedat     time.time     `json:"updated_at"`
    deletedat     sql.nulltime  `json:"deleted_at"`
}

var db *gorm.db

func main() {
    databaseconfig := fmt.sprintf("%s:%s@tcp(%s:%s)/%s?multistatements=true&parsetime=true", "root", "", "127.0.0.1", "3306", "tester")

    db, _ = gorm.open(mysql.open(databaseconfig), &gorm.config{
        logger: logger.default.logmode(logger.info),
    })
    sqldb, _ := db.db()
    defer sqldb.close()

    db.automigrate(&parcelorder{}, &parcelorderdetails{})

    order := parcelorder{
        deliveryaddress: "dummy address",
        pickupaddress:   "dummy pickup address",
        orderid:         "unique-order-id-1",
        senderid:        1,
        parcelorderdetails: &parcelorderdetails{
            status: 0,
        },
    }
    db.create(&order)
}

记录：

2021/11/23 20:57:53 D:/go/src/udemy-solving/00003/main.go:62
[0.780ms] [rows:1] INSERT INTO `parcel_order_details` (`created_at`,`updated_at`,`deleted_at`,`biker_id`,`parcel_order_id`,`pickup_time`,`delivery_time`,`status`) VALUES ('2021-11-23 20:57:53.393','2021-11-23 20:57:53.393',NULL,NULL,4,NULL,NULL,0) ON DUPLICATE KEY UPDATE `parcel_order_id`=VALUES(`parcel_order_id`)

2021/11/23 20:57:53 D:/go/src/udemy-solving/00003/main.go:62
[14.900ms] [rows:1] INSERT INTO `parcel_orders` (`created_at`,`updated_at`,`deleted_at`,`sender_id`,`order_id`,`pickup_address`,`delivery_address`) VALUES ('2021-11-23 20:57:53.392','2021-11-23 20:57:53.392',NULL,1,'unique-order-id-1','dummy pickup address','dummy address')

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