How to do gin-validation for an array of struct

[NishantG01]

Hi @Depado , Greetings, I saw your blog for gin-validation and it helped in my use case. But I am unable to use it if the validation is done on an array of struct.

My sample code

package main

import (
    "encoding/json"
    "errors"
    "fmt"
    "net/http"
    "reflect"
    "strings"

    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
    "github.com/go-playground/validator/v10"
)

type User struct {
    Email string `json:"email" form:"e-mail" binding:"required"`
    Name  string `json:"name" binding:"required"`
}

func main() {
    route := gin.Default()
    if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
        v.RegisterTagNameFunc(func(fld reflect.StructField) string {
            name := strings.SplitN(fld.Tag.Get("json"), ",", 2)[0]
            if name == "-" {
                return ""
            }
            return name
        })
    }
    route.POST("/user", validateUser)
    route.Run(":8085")
}
func validateUser(c *gin.Context) {
    var u []User
    if err := c.ShouldBindJSON(&u); err == nil {
        c.JSON(http.StatusOK, gin.H{"message": "User validation successful."})
    } else {
        fmt.Println(err)
        var verr validator.ValidationErrors
        var jsErr *json.UnmarshalTypeError

        if errors.As(err, &verr) {
            c.JSON(http.StatusBadRequest, gin.H{"errors": Descriptive(verr)})
            return
        } else if errors.As(err, &jsErr) {
            c.JSON(http.StatusBadRequest, gin.H{"errors": MarshalErr(*jsErr)})
            return
        }
    }
}

func Simple(verr validator.ValidationErrors) map[string]string {
    errs := make(map[string]string)
    for _, f := range verr {
        err := f.ActualTag()

        if f.Param() != "" {
            err = fmt.Sprintf("%s=%s", err, f.Param())
        }
        errs[f.Field()] = err + "," + f.Kind().String()
        fmt.Println(errs)
    }
    return errs

}

type ValidationError struct {
    Field  string `json:"field"`
    Type   string `json:"type"`
    Reason string `json:"reason"`
}
func MarshalErr(jsErr json.UnmarshalTypeError) ValidationError {
    errs := ValidationError{}
    errs.Field=jsErr.Field
    errs.Reason="invalid type"
    errs.Type=jsErr.Type.String()
    return errs
}
func Descriptive(verr validator.ValidationErrors) []ValidationError {
    errs := []ValidationError{}

    for _, f := range verr {
        fmt.Println(f)
        err := f.ActualTag()
        if f.Param() != "" {
            err = fmt.Sprintf("%s=%s", err, f.Param())
        }
        errs = append(errs, ValidationError{Field: f.Field(), Reason: err, Type: f.Type().Name()})
    }

    return errs
}

Test Input

curl --location --request POST 'http://localhost:8085/user' \
--header 'content-type: application/json' \
--data-raw '[
    {
        "email": "me@example.com",
        "name": "Me"
    },
    {
        "email": "me@example.com"
    }
]'

Expected output

"errors": [
        {
            "field": "name",
            "type": "string",
            "reason": "required"
        }
    ]

Can you please help me with it.