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build-web-application-with-golang | A golang ebook intro how to build a web | Learning library

 by   astaxie Go Version: Current License: BSD-3-Clause

 by   astaxie Go Version: Current License: BSD-3-Clause

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kandi X-RAY | build-web-application-with-golang Summary

build-web-application-with-golang is a Go library typically used in Tutorial, Learning applications. build-web-application-with-golang has no bugs, it has no vulnerabilities, it has a Permissive License and it has medium support. You can download it from GitHub.
A golang ebook intro how to build a web with golang
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Security
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kandi-support Support

  • build-web-application-with-golang has a medium active ecosystem.
  • It has 38531 star(s) with 10235 fork(s). There are 2460 watchers for this library.
  • It had no major release in the last 12 months.
  • There are 105 open issues and 181 have been closed. On average issues are closed in 222 days. There are no pull requests.
  • It has a neutral sentiment in the developer community.
  • The latest version of build-web-application-with-golang is current.
This Library - Support
Best in #Learning
Average in #Learning
This Library - Support
Best in #Learning
Average in #Learning

quality kandi Quality

  • build-web-application-with-golang has no bugs reported.
This Library - Quality
Best in #Learning
Average in #Learning
This Library - Quality
Best in #Learning
Average in #Learning

securitySecurity

  • build-web-application-with-golang has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
This Library - Security
Best in #Learning
Average in #Learning
This Library - Security
Best in #Learning
Average in #Learning

license License

  • build-web-application-with-golang is licensed under the BSD-3-Clause License. This license is Permissive.
  • Permissive licenses have the least restrictions, and you can use them in most projects.
This Library - License
Best in #Learning
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This Library - License
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buildReuse

  • build-web-application-with-golang releases are not available. You will need to build from source code and install.
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This Library - Reuse
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build-web-application-with-golang Key Features

A golang ebook intro how to build a web with golang

build-web-application-with-golang Examples and Code Snippets

See all related Code Snippets

Go Deep understanding of custom error handling in REST API

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type A int
type Person struct{}
package main

import (
    "errors"
    "fmt"
)

type IntFun func(a,b int) error
func main(){
    var addFunc IntFun
    addFunc = func(a, b int) error {
        if a ==0 || b == 0 {
            return errors.New(`zero valued inputs`)
        }
        fmt.Println(`sum := `, a+b)
        return nil
    }

    addFunc.Add(5, 3) //Output: sum :=  8
    addFunc.Add(0, 0) //Output: zero valued inputs
}

func (fn IntFun) Add(a, b int)  {
    err := fn(a,b)
    if err != nil {
        fmt.Println(err)
        return
    }
}
func init() {
    http.Handle("/view", appHandler(viewRecord))
}
type A int
type Person struct{}
package main

import (
    "errors"
    "fmt"
)

type IntFun func(a,b int) error
func main(){
    var addFunc IntFun
    addFunc = func(a, b int) error {
        if a ==0 || b == 0 {
            return errors.New(`zero valued inputs`)
        }
        fmt.Println(`sum := `, a+b)
        return nil
    }

    addFunc.Add(5, 3) //Output: sum :=  8
    addFunc.Add(0, 0) //Output: zero valued inputs
}

func (fn IntFun) Add(a, b int)  {
    err := fn(a,b)
    if err != nil {
        fmt.Println(err)
        return
    }
}
func init() {
    http.Handle("/view", appHandler(viewRecord))
}
type A int
type Person struct{}
package main

import (
    "errors"
    "fmt"
)

type IntFun func(a,b int) error
func main(){
    var addFunc IntFun
    addFunc = func(a, b int) error {
        if a ==0 || b == 0 {
            return errors.New(`zero valued inputs`)
        }
        fmt.Println(`sum := `, a+b)
        return nil
    }

    addFunc.Add(5, 3) //Output: sum :=  8
    addFunc.Add(0, 0) //Output: zero valued inputs
}

func (fn IntFun) Add(a, b int)  {
    err := fn(a,b)
    if err != nil {
        fmt.Println(err)
        return
    }
}
func init() {
    http.Handle("/view", appHandler(viewRecord))
}

See all related Code Snippets

Community Discussions

Trending Discussions on build-web-application-with-golang
  • Go Deep understanding of custom error handling in REST API
Trending Discussions on build-web-application-with-golang

QUESTION

Go Deep understanding of custom error handling in REST API

Asked 2021-May-07 at 05:10

I am coming from the world of Node.js where I learn a lot from building web application using Express and there, there is a good way, I think, to handle when dealing with error and in case of unexpected error, there is a awesome way to catch it.

So, I looked for the same thing in Go. I don't know if I have already found it, but what I found come from this link https://astaxie.gitbooks.io/build-web-application-with-golang/content/en/11.1.html and from some articles I read, it seems like many developers are using the same approach.

My concern, and not a real one, is that I don't understand some part of that code below.

type appHandler func(http.ResponseWriter, *http.Request) error

func (fn appHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    if err := fn(w, r); err != nil {
        http.Error(w, err.Error(), 500)
    }
}

I know that it's possible to create custom type in go, but seriously I don't understand what this one means or how to understand it in the http.Serve

type appHandler func(http.ResponseWriter, *http.Request) error

and one of the thing that I don't catch is

func (fn AppHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {

In most of the code I read, generally, it's a struct or a replaced type (I mean type Account int) but here, it's a function. I would like to understand how is it going to help in handling errors.

Inside the implementation of the ServeHTTP up there, we have this line err := fn(w, r). Please, can you explain it?

From the same article, we have this code

func viewRecord(w http.ResponseWriter, r *http.Request) error {
    c := appengine.NewContext(r)
    key := datastore.NewKey(c, "Record", r.FormValue("id"), 0, nil)
    record := new(Record)
    if err := datastore.Get(c, key, record); err != nil {
        return err
    }
    return viewTemplate.Execute(w, record)
}

and this line

func init() {
    http.Handle("/view", appHandler(viewRecord))
}

Please, could you help me to understand this appHandler(viewRecord)? What is it exactly? It is an instantiation, is it casting? What is it supposed to do? I mean, how to understand that line that seems critical?

One last question, please. Is it possible to catch an error that might happen anywhere during the treatment of a request? In Node.js, you can just do something like

const app = express()

const errorHandler = (
  err: Error,
  req: Request,
  res: Response,
  next: NextFunction
) => {
  if (err instanceof CustomError) {
    return res.status(err.statusCode).send({ errors: err.serializeErrors() });
  }
  
  res.status(500).send({ 
    errors: [{ message: err.message || 'Something went wrong' }]
  });
}

app.use(errorHandler())

Something like that, is it possible in Go?

Thank you.

ANSWER

Answered 2021-May-07 at 05:10

In Go, we can define custom types from any primitive types, example:

type A int
type Person struct{}

This is common for functions al well. You can define a Go type with desired function signature like in appHandler type in above example. I have added simple example below.

package main

import (
    "errors"
    "fmt"
)

type IntFun func(a,b int) error
func main(){
    var addFunc IntFun
    addFunc = func(a, b int) error {
        if a ==0 || b == 0 {
            return errors.New(`zero valued inputs`)
        }
        fmt.Println(`sum := `, a+b)
        return nil
    }

    addFunc.Add(5, 3) //Output: sum :=  8
    addFunc.Add(0, 0) //Output: zero valued inputs
}

func (fn IntFun) Add(a, b int)  {
    err := fn(a,b)
    if err != nil {
        fmt.Println(err)
        return
    }
}

and also refer user-defined-function-type-go

In your case,

func init() {
    http.Handle("/view", appHandler(viewRecord))
}

This is the http endpoint handling part. "/view" is the path pattern and other argument is the handler for the request. That parameter should implement Handler interface in net/http Go package. So that's why app handler type have ServeHttp function.

viewRecord function is also compatible with type appHandler function type. it handle the request coming to "/view" endpoint. So it is casted to appHandler type and passed to http.Handle("/view", appHandler(viewRecord)) Handle function.

I think this will explain the scenario. Please comment if anything not clear.

Source https://stackoverflow.com/questions/67428860

Community Discussions, Code Snippets contain sources that include Stack Exchange Network

Vulnerabilities

No vulnerabilities reported

Install build-web-application-with-golang

You can download it from GitHub.

Support

For any new features, suggestions and bugs create an issue on GitHub. If you have any questions check and ask questions on community page Stack Overflow .

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