search
HomeBackend DevelopmentGolangGo - Error. Unable to unpack custom error type

Go - Error. Unable to unpack custom error type

Feb 09, 2024 pm 04:45 PM
go language

Go - 错误。无法解包自定义错误类型

php editor Xigua introduces to you: In Go language, when we use custom error types, we sometimes encounter "Error. Unable to unpack custom error type" question. This problem usually occurs when we try to pass custom error types to other functions or methods. While this may seem like a tricky problem, there are actually several ways to go about it. In this article, we will explore the causes of this problem and provide solutions to help you solve this problem.

Question content

I'm trying to use the go stdlib package errors to unpack a custom error type using errors.as, but it seems the check is failing and I can't extract the underlying error .

I extracted a minimal reproducible example:

package main

import (
    "errors"
    "fmt"
)

type myError struct {
    err error
}

func (m myError) Error() string {
    return fmt.Sprintf("my error: %s", m.err)
}

func retError() error {
    return &myError{errors.New("wrapped")}
}

func main() {
    var m myError
    if err := retError(); errors.As(err, &m) {
        fmt.Println("unwrapped", m.err)
    } else {
        fmt.Println(err)
    }
}

https://go.dev/play/p/i7bnk4-rdib - Examples on the go playground. If launched, it prints "my error: wrapping" instead of the expected "unwrapped wrapping".

The example in the errors.as documentation works, I can't seem to understand what I'm doing wrong - I pass *myerror to errors.as and that seems to be Correct (because passing myerror causes a panic: target must be a non-zero pointer , which is expected).

Solution

instead of:

func reterror() error {
    return &myerror{errors.new("wrapped")}
}

Do:

func retError() error {
    return myError{errors.New("wrapped")}
}

The above is the detailed content of Go - Error. Unable to unpack custom error type. For more information, please follow other related articles on the PHP Chinese website!

Statement
This article is reproduced at:stackoverflow. If there is any infringement, please contact admin@php.cn delete
Go vs. Other Languages: A Comparative AnalysisGo vs. Other Languages: A Comparative AnalysisApr 28, 2025 am 12:17 AM

Goisastrongchoiceforprojectsneedingsimplicity,performance,andconcurrency,butitmaylackinadvancedfeaturesandecosystemmaturity.1)Go'ssyntaxissimpleandeasytolearn,leadingtofewerbugsandmoremaintainablecode,thoughitlacksfeatureslikemethodoverloading.2)Itpe

Comparing init Functions in Go to Static Initializers in Other LanguagesComparing init Functions in Go to Static Initializers in Other LanguagesApr 28, 2025 am 12:16 AM

Go'sinitfunctionandJava'sstaticinitializersbothservetosetupenvironmentsbeforethemainfunction,buttheydifferinexecutionandcontrol.Go'sinitissimpleandautomatic,suitableforbasicsetupsbutcanleadtocomplexityifoverused.Java'sstaticinitializersoffermorecontr

Common Use Cases for the init Function in GoCommon Use Cases for the init Function in GoApr 28, 2025 am 12:13 AM

ThecommonusecasesfortheinitfunctioninGoare:1)loadingconfigurationfilesbeforethemainprogramstarts,2)initializingglobalvariables,and3)runningpre-checksorvalidationsbeforetheprogramproceeds.Theinitfunctionisautomaticallycalledbeforethemainfunction,makin

Channels in Go: Mastering Inter-Goroutine CommunicationChannels in Go: Mastering Inter-Goroutine CommunicationApr 28, 2025 am 12:04 AM

ChannelsarecrucialinGoforenablingsafeandefficientcommunicationbetweengoroutines.Theyfacilitatesynchronizationandmanagegoroutinelifecycle,essentialforconcurrentprogramming.Channelsallowsendingandreceivingvalues,actassignalsforsynchronization,andsuppor

Wrapping Errors in Go: Adding Context to Error ChainsWrapping Errors in Go: Adding Context to Error ChainsApr 28, 2025 am 12:02 AM

In Go, errors can be wrapped and context can be added via errors.Wrap and errors.Unwrap methods. 1) Using the new feature of the errors package, you can add context information during error propagation. 2) Help locate the problem by wrapping errors through fmt.Errorf and %w. 3) Custom error types can create more semantic errors and enhance the expressive ability of error handling.

Security Considerations When Developing with GoSecurity Considerations When Developing with GoApr 27, 2025 am 12:18 AM

Gooffersrobustfeaturesforsecurecoding,butdevelopersmustimplementsecuritybestpracticeseffectively.1)UseGo'scryptopackageforsecuredatahandling.2)Manageconcurrencywithsynchronizationprimitivestopreventraceconditions.3)SanitizeexternalinputstoavoidSQLinj

Understanding Go's error InterfaceUnderstanding Go's error InterfaceApr 27, 2025 am 12:16 AM

Go's error interface is defined as typeerrorinterface{Error()string}, allowing any type that implements the Error() method to be considered an error. The steps for use are as follows: 1. Basically check and log errors, such as iferr!=nil{log.Printf("Anerroroccurred:%v",err)return}. 2. Create a custom error type to provide more information, such as typeMyErrorstruct{MsgstringDetailstring}. 3. Use error wrappers (since Go1.13) to add context without losing the original error message,

Error Handling in Concurrent Go ProgramsError Handling in Concurrent Go ProgramsApr 27, 2025 am 12:13 AM

ToeffectivelyhandleerrorsinconcurrentGoprograms,usechannelstocommunicateerrors,implementerrorwatchers,considertimeouts,usebufferedchannels,andprovideclearerrormessages.1)Usechannelstopasserrorsfromgoroutinestothemainfunction.2)Implementanerrorwatcher

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

mPDF

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Atom editor mac version download

Atom editor mac version download

The most popular open source editor

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)