golang GORM和Gin无法创建具有关联的对象

问题内容

我使用 GORM 作为 ORM 以及我的 Golang API 来与我的数据库进行通信。

但是对于创建与数据库关联的实体，代码失败了（DB.Create(&data))：

2023/11/01 20:44:14 [Recovery] 2023/11/01 - 20:44:14 panic recovered:POST /v1/product/products HTTP/1.1Host: localhost:8080Accept: */*Content-Length: 589Content-Type: application/jsonUser-Agent: curl/8.4.0runtime error: invalid memory address or nil pointer dereference/usr/lib/go/src/runtime/panic.go:261 (0x452d97)        panicmem: panic(memoryError)/usr/lib/go/src/runtime/signal_unix.go:861 (0x452d65)        sigpanic: panicmem()/home/grimm/go/pkg/mod/gorm.io/[email protected]/finisher_api.go:18 (0x926e7c)        (*DB).Create: if db.CreateBatchSize > 0 {/home/grimm/Documents/beeskill/website/back_end/API_website/main.go:122 (0x99cfab)        CreatingProduct: DB.Create(&data)/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/context.go:174 (0x8c9ad9)        (*Context).Next: c.handlers[c.index](c)/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/recovery.go:102 (0x8c9ac7)        CustomRecoveryWithWriter.func1: c.Next()/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/context.go:174 (0x8c8c7d)        (*Context).Next: c.handlers[c.index](c)/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/logger.go:240 (0x8c8c4c)        LoggerWithConfig.func1: c.Next()/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/context.go:174 (0x8c7d3a)        (*Context).Next: c.handlers[c.index](c)/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/gin.go:620 (0x8c79cd)        (*Engine).handleHTTPRequest: c.Next()/home/grimm/go/pkg/mod/github.com/gin-gonic/[email protected]/gin.go:576 (0x8c74fc)        (*Engine).ServeHTTP: engine.handleHTTPRequest(c)/usr/lib/go/src/net/http/server.go:2938 (0x6a35ed)        serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)/usr/lib/go/src/net/http/server.go:2009 (0x69f4d3)        (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)/usr/lib/go/src/runtime/asm_amd64.s:1650 (0x46ed20)        goexit: BYTE    $0x90   // NOP

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使用的代码：

package mainimport (    "net/http"    "github.com/gin-gonic/gin"    "gorm.io/driver/sqlite"    "gorm.io/gorm")type CategoryProduct struct {    gorm.Model    Title       string `json:"title" gorm:"not null"`    Description string `json:"description"`}type CreateCategoryProduct struct {    gorm.Model    Title       string `json:"title" binding:"required"`    Description string `json:"description" binding:"required"`}// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------type PriceYearProduct struct {    gorm.Model    Price       float64 `json:"price" gorm:"not null"`    Description string  `json:"description"`}type CreatePriceYearProduct struct {    gorm.Model    Price       float64 `json:"price" binding:"required"`    Description string  `json:"description" binding:"required"`}// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------type PriceMounthProduct struct {    gorm.Model    Price       float64 `json:"price" gorm:"not null"`    Description string  `json:"description"`}type CreatePriceMounthProduct struct {    gorm.Model    Price       float64 `json:"price" binding:"required"`    Description string  `json:"description" binding:"required"`}// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------// --------------------------------------------------------type Product struct {    gorm.Model    Name               string             `json:"name" gorm:"not null"`    Description        string             `json:"description" gorm:"not null"`    PriceMounthProduct PriceMounthProduct `json:"pricemounth"`    PriceYearProduct   PriceYearProduct   `json:"priceyear"`    CategoryProduct    CategoryProduct    `json:"category"`}type CreateProduct struct {    gorm.Model    Name               string             `json:"name" binding:"required"`    Description        string             `json:"description" binding:"required"`    PriceMounthProduct PriceMounthProduct `json:"pricemounth" binding:"required"`    PriceYearProduct   PriceYearProduct   `json:"priceyear" binding:"required"`    CategoryProduct    CategoryProduct    `json:"category" binding:"required"`}var DB *gorm.DBfunc ConnectDatabase() {    database, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})    if err != nil {        panic("Failed to connect to database!")    }    // For the product and dependancies of them    err = database.AutoMigrate(&CategoryProduct{}, &PriceYearProduct{}, &PriceMounthProduct{})    if err != nil {        return    }    err = database.AutoMigrate(&Product{})    if err != nil {        return    }    DB = database}// POST /v1/products// Create a productfunc CreatingProduct(c *gin.Context) {    // Validate input    var input CreateProduct    if err := c.ShouldBindJSON(&input); err != nil {        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})        return    }    data := Product{        Name:               input.Name,        Description:        input.Description,        PriceYearProduct:   input.PriceYearProduct,        PriceMounthProduct: input.PriceMounthProduct,        CategoryProduct:    input.CategoryProduct,    }    DB.Create(&data)    c.JSON(http.StatusOK, gin.H{"data": data})}func Routes() {    var router = gin.Default()    v1 := router.Group("/v1")    {        //Product CRUD        product := v1.Group("/product")        product.POST("/products", CreatingProduct)    }    err := router.Run(":8080")    if err != nil {        return    }}func main() {    ConnectDatabase()    Routes()}

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以及用于发布一些数据的curl命令：

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curl http://localhost:8080/v1/product/products --request "POST" --header "Content-Type: application/json" --data @file.json

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file.json 的内容：

{    "name": "airplane simulation",    "description": "airplane simulation for everybody, childrens to adults.",    "priceyear": {      "price": 44.99,      "description": "pay for a year to access on irplane simulation for everybody, childrens to adults."    },    "pricemounth": {      "price": 4.99,      "description": "pay for a mounth to access on irplane simulation for everybody, childrens to adults."    },    "category": {      "title": "Airplane",      "description": "Information cataegorized on airplane."    }}

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我查看了官方文档，但没有更多信息……尝试使用创建时的变量进行调试，但一切似乎都很好……

解决方法

运行代码出现错误

[error] invalid field found for struct main.Product's field PriceMounthProduct: define a valid foreign key for relations or implement the Valuer/Scanner interface

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gin日志前第一行的错误信息，可能你错过了。

所以修复它，在 Product 结构中添加正确的 foreignkey gorm 标签 就可以了。

type Product struct {    gorm.Model    Name               string             `json:"name" gorm:"not null"`    Description        string             `json:"description" gorm:"not null"`    PriceMounthProduct PriceMounthProduct `json:"pricemounth" gorm:"foreignkey:ID"`    PriceYearProduct   PriceYearProduct   `json:"priceyear" gorm:"foreignkey:ID"`    CategoryProduct    CategoryProduct    `json:"category" gorm:"foreignkey:ID"`}

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然后运行

curl http://localhost:8080/v1/product/products --request "POST" --header "Content-Type: application/json" --data @info.json

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得到了

{"data":{"ID":1,"CreatedAt":"2023-11-02T13:37:24.052228+08:00","UpdatedAt":"2023-11-02T13:37:24.052228+08:00","DeletedAt":null,"name":"airplane simulation","description":"airplane simulation for everybody, childrens to adults.","pricemounth":{"ID":1,"CreatedAt":"2023-11-02T13:37:24.054792+08:00","UpdatedAt":"2023-11-02T13:37:24.054792+08:00","DeletedAt":null,"price":4.99,"description":"pay for a mounth to access on irplane simulation for everybody, childrens to adults."},"priceyear":{"ID":1,"CreatedAt":"2023-11-02T13:37:24.056352+08:00","UpdatedAt":"2023-11-02T13:37:24.056352+08:00","DeletedAt":null,"price":44.99,"description":"pay for a year to access on irplane simulation for everybody, childrens to adults."},"category":{"ID":1,"CreatedAt":"2023-11-02T13:37:24.056585+08:00","UpdatedAt":"2023-11-02T13:37:24.056585+08:00","DeletedAt":null,"title":"Airplane","description":"Information cataegorized on airplane."}}}% 

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