How to return struct from golang error method

Question

I am writing a simple rest api using echo framework for route handling. I am trying to maintain centralised error handling using middlewares. In the following code, in the error method implementation I want to return a struct so that I can use that info in custom error Handler

main.go

package main
import log "github.com/sirupsen/logrus"
import "github.com/labstack/echo"
import "net/http"
import "fmt"

func main(){
e := echo.New()
e.GET("process", PostHandler)
e.HTTPErrorHandler = customHTTPErrorHandler

log.Fatal(e.Start(":3000"))
}

func PostHandler(ctx echo.Context) error{
 x:= 0;
 if x != 0 {
    return  NewTypeError(1024, "Invalid arguments")
 }
 return ctx.JSON(http.StatusOK, "message")
}

func customHTTPErrorHandler(err error, c echo.Context) {
    fmt.Println("Inside custom error")
    fmt.Println(err);
}

error.go

package main
import "fmt"
type Error struct{
    Message string
    Internal int
}

func (e *Error)Error() string{
    fmt.Println("Hello error")
    return "error"
}

func NewTypeError( Internal int, Message string) *Error {
    fmt.Println(Internal)
    fmt.Println(Message)
    return &Error{
        
        Message,
        Internal,
       
    }
}

I want my output json response to be sent from custom error middleware like this.

{
code: "1024",
message: "Invalid Arguments"
}

Anderson F. Viana · Accepted Answer · 2022-03-15 01:36:01Z

2

Add c.JSON to customHTTPErrorHandler and add json tags to struct Error.

// main.go

package main

import (
    "fmt"
    "net/http"

    "github.com/labstack/echo"
    log "github.com/sirupsen/logrus"
)

func main() {
    e := echo.New()
    e.GET("process", PostHandler)
    e.HTTPErrorHandler = customHTTPErrorHandler

    log.Fatal(e.Start(":3000"))
}

func PostHandler(ctx echo.Context) error {
    x := 0
    if x == 0 {
        return NewTypeError(http.StatusInternalServerError, 1024, "Invalid arguments")
    }
    return ctx.JSON(http.StatusOK, "message")
}

func customHTTPErrorHandler(err error, c echo.Context) {
    fmt.Println("Inside custom error")

    var rerr *Error

    switch e := err.(type) {
    case *Error:
        rerr = e
    case *echo.HTTPError:
        // todo: improve error conversion
        rerr = NewTypeError(e.Code, EchoHttpError, e.Error())
    default:
        rerr = NewTypeError(http.StatusInternalServerError, InternalError, e.Error())
    }

    c.JSON(rerr.Code, rerr)
}

// error.go

package main

import (
    "fmt"
)

const (
    EchoHttpError int = iota
    InternalError
)

type Error struct {
    Code     int    `json:"-"` // optional
    Message  string `json:"message"`
    Internal int    `json:"internal"`
}

func (e *Error) Error() string {
    fmt.Println("Hello error")
    return "error"
}

func NewTypeError(code int, internal int, message string) *Error {
    fmt.Println(internal)
    fmt.Println(message)
    return &Error{
        Code:     code,
        Message:  message,
        Internal: internal,
    }
}

answered Mar 15, 2022 at 1:36

Anderson F. Viana

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1 Comment

user846445 Over a year ago

Does the Error() method still remains the same. Its return type should be struct right . Else in middleware we receive only string "error" based on above implementation.

Arif Aminudin · Accepted Answer · 2022-03-15 03:55:45Z

2

you should insert model on argument. and u should make variable response, same with struct. if u show code on response, u should add code on error struct.

func ToErrorResponse(err model.Error) *ErrorResponse {
    errorResponse := &ErrorResponse{
        code:       err.Code,
        message: err.Message,
    }
    return errorResponse
}

and call function.

answered Mar 15, 2022 at 3:55

Arif Aminudin

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