Gorm and Gin error 500 only when Updating

Issue

I’ve a pretty simple CRUD for a Task list, and so far I’m able to Create, List all, List by ID and Delete records, bu when I try to update, it gives me the following error:

go-proj          | reflect: call of reflect.Value.Field on string Value
go-proj          | /usr/local/go/src/reflect/value.go:850 (0x4a2464)
go-proj          |      Value.Field: panic(&ValueError{"reflect.Value.Field", v.kind()})
go-proj          | /go/pkg/mod/gorm.io/gorm@v1.20.7/schema/field.go:393 (0x996e50)
go-proj          |      (*Field).setupValuerAndSetter.func2: fieldValue := reflect.Indirect(value).Field(field.StructField.Index[0]).Field(field.StructField.Index[1])
go-proj          | /go/pkg/mod/gorm.io/gorm@v1.20.7/callbacks/update.go:230 (0xb3e3f0)
go-proj          |      ConvertToAssignments: value, isZero := field.ValueOf(updatingValue)
go-proj          | /go/pkg/mod/gorm.io/gorm@v1.20.7/callbacks/update.go:64 (0xb3bfd9)
go-proj          |      Update: if set := ConvertToAssignments(db.Statement); len(set) != 0 {
go-proj          | /go/pkg/mod/gorm.io/gorm@v1.20.7/callbacks.go:105 (0x9a5b7c)
go-proj          |      (*processor).Execute: f(db)
go-proj          | /go/pkg/mod/gorm.io/gorm@v1.20.7/finisher_api.go:303 (0x9ad886)
go-proj          |      (*DB).Updates: tx.callbacks.Update().Execute(tx)
go-proj          | /app/app/controllers/listController.go:70 (0xb49c7b)
go-proj          |      Update: if err := models.DB.Model(&list).Updates(input).Error; err != nil {
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x93d01a)
go-proj          |      (*Context).Next: c.handlers[c.index](c)
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/recovery.go:83 (0x951004)
go-proj          |      RecoveryWithWriter.func1: c.Next()
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x93d01a)
go-proj          |      (*Context).Next: c.handlers[c.index](c)
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/logger.go:241 (0x950104)
go-proj          |      LoggerWithConfig.func1: c.Next()
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x93d01a)
go-proj          |      (*Context).Next: c.handlers[c.index](c)
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/gin.go:409 (0x947359)
go-proj          |      (*Engine).handleHTTPRequest: c.Next()
go-proj          | /go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/gin.go:367 (0x946a4c)
go-proj          |      (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
go-proj          | /usr/local/go/src/net/http/server.go:2843 (0x6cd7c2)
go-proj          |      serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
go-proj          | /usr/local/go/src/net/http/server.go:1925 (0x6c8ecc)
go-proj          |      (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
go-proj          | /usr/local/go/src/runtime/asm_amd64.s:1374 (0x46cba0)
go-proj          |      goexit: BYTE    $0x90   // NOP
go-proj          | 
go-proj-nginx    | 172.27.0.1 - - [20/Nov/2020:17:32:56 +0000] "PUT /list/3 HTTP/1.1" 500 0 "-" "PostmanRuntime/7.6.0"

I’ve tried changing versions of both frameworks Gorm and Gin

I’ll be extracting the only parts of my code that matters:

Router:

r := gin.Default()

r.PUT("/list/:id", controllers.Update)

Model:

type List struct {
    gorm.Model
    UserId uint
    Title  string
    Status uint
}

Controller:

type UpdateListInput struct {
        Title  string `json:"title"`
        Status uint   `json:"status"`
}

func Update(c *gin.Context) {
        var list models.List

        if err := models.DB.Where("id = ?", c.Param("id")).First(&list).Error; err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": "Record not found"})
                return
        }

        var input UpdateListInput
        if err := c.ShouldBindJSON(&input); err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
                return
        }

        if err := models.DB.Model(&list).Updates(input).Error; err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
        }

        c.JSON(http.StatusOK, gin.H{"data": list})
}

I’m sending the following JSON to /list/:id:

{
    "title": "Shopping List 2",
    "status": 2
}

For more info you can check my repo’s folder .docker/ on GitHub, maybe I’ve messed something on Nginx, Postgres or even Golang configuration, because I’m running my app on containers.

Edit1:
I’ve managed it to work by hard coding the data to be updated in my controller:

func Update(c *gin.Context) {                                  
     var list models.List                                  
     if err := models.DB.Where("id = ?", c.Param("id")).First(&list).Error; err != nil {                                  
         c.JSON(http.StatusBadRequest, gin.H{"error": "Record not found"})                                  
         return                                  
     }                                  
                                   
     input := map[string]interface{}{                                        
         "title":  "AAAAAAAAAa",                                                                                                                         
         "status": 3,                                                                                                                                    
     }                                                                                                                                                   
     if err := models.DB.Model(&list).Updates(input).Error; err != nil {                                                                                 
         c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})                                                                                      
         return                                                                                                                                          
     }                                                                                                                                                   
                                                                                       
      c.JSON(http.StatusOK, gin.H{"data": list})
}  

Solution

Well, it’s a workaround, probably I will be opening an issue on Gorm’s Github because I don’t think that this is the right way of doing it, the only thing that I’d to do is convert from UpdateListInput struct to a variable of map[string]interface{} using reflect package

Here’s my controller:

func Update(c *gin.Context) {
        var list models.List
        if err := models.DB.Where("id = ?", c.Param("id")).First(&list).Error; err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": "Record not found"})
                return
        }

        var input UpdateListInput
        if err := c.ShouldBindJSON(&input); err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
                return
        }
        v := reflect.ValueOf(input)
        typeOfV := v.Type()

        inputData := map[string]interface{}{}

        for i := 0; i < v.NumField(); i++ {
                inputData[typeOfV.Field(i).Name] = v.Field(i).Interface()
        }

        if err := models.DB.Model(&list).Updates(inputData).Error; err != nil {
                c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
                return
        }

        c.JSON(http.StatusOK, gin.H{"data": list})
}

Answered By – Rafael Breno

Answer Checked By – Robin (GoLangFix Admin)

Leave a Reply

Your email address will not be published.