Parsing array form elements with bindings

Question

I am trying to submit and parse a form in go and I am failing to parse the form fields properly. Here is an excerpt of the code I am trying.

formtest.go : package main

import (
    "fmt"
    "log"
    "net/http"

    "github.com/codegangsta/negroni"
    "github.com/davecgh/go-spew/spew"
    "github.com/julienschmidt/httprouter"
    "github.com/mholt/binding"
    "gopkg.in/unrolled/render.v1"
)

type FormInfo struct {
    Fields    []string
    Action    string
    PageTitle string
    Id        string
}

func (f *FormInfo) FieldMap(*http.Request) binding.FieldMap {
    return binding.FieldMap{
        &f.Fields: "fields",
        &f.Action: "action",
    }
}

func formtest(
    resp http.ResponseWriter,
    req *http.Request,
    p httprouter.Params) {

    // var ticket Ticket
    info := new(FormInfo)
    tkt := p.ByName("tkt")
    info.PageTitle = tkt
    info.Id = tkt

    if req.Method == "POST" {
        bind_err := binding.Bind(req, info)
        if bind_err.Handle(resp) {
            log.Println("Error decoding form contents")
            return
        }
        spew.Dump(info)
    }

    Render.HTML(resp, http.StatusOK, "formtest", info)
    return
}

var Render *render.Render

func main() {

    router := httprouter.New()

    router.GET("/formtest", formtest)
    router.POST("/formtest", formtest)

    Render = render.New(render.Options{
        Layout:          "layout",
        IndentJSON:      true,
        IndentXML:       true,
        HTMLContentType: "text/html",
        IsDevelopment:   true,
    })

    n := negroni.New(
        negroni.NewRecovery(),
        negroni.NewLogger(),
        negroni.NewStatic(http.Dir("static")),
    )
    n.UseHandler(router)
    n.Run(fmt.Sprintf(":%d", 3000))

}

templates/layout.tmpl :

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>{{ .PageTitle }}</title>
    <meta http-equiv="Content-Type" content="text/html;" charset="utf-8">
    <meta charset="UTF-8">
    <link rel="shortcut icon" type="image/x-icon" href="/favicon.ico" />
    <link rel="apple-touch-icon" href="/mobile.png" />
    <meta name="viewport" 
          content="initial-scale=1.0,width=device-width,user-scalable=no">
    <meta name="generator" content="Go">
    <link rel="stylesheet" href="/base.css" type="text/css">
  </head>

  <body>

      <div class="mainbody">
        {{ yield }}
      </div>

  </body>

</html>

templates/formtest.tmpl :

<h1>{{ .PageTitle }}</h1>

<form action="/formtest/{{ .Id }}" method="POST">

    <div class="details">
      <label>Question 1</label>
      <input type="text" name="fields[0]" value="value 1" />
    </div>

    <div class="details">
      <label>Question 2</label>
      <input type="text" name="fields[1]" value="value 2" />
    </div>

    <div class="details">
      <input type="submit" name="action" value="save" />
    </div>

</form>

Procedure:

go run formtest.go
Open browser and go to http://127.0.0.1:3000/formtest
Submit the form
Check console for the logs.

Observation :

(*main.FormInfo)(0xc820066c30)({
 Fields: ([]string) <nil>,
 Action: (string) (len=4) "save",
 PageTitle: (string) "",
 Id: (string) ""
})

Expectation :

Fields: ([]string) <contains two values submitted>,

But when I try to print the contents of Fields, it is nil. What am I doing wrong?

provide MCVE stackoverflow.com/help/mcve . Now you code not correct. — user4651282
– user4651282, Commented Sep 28, 2015 at 11:57
I will try to answer. Why do you use so many libraries for this simple example? — user4651282
– user4651282, Commented Sep 29, 2015 at 0:00

score 1 · Accepted Answer · 2015-09-29 11:59:12Z

1

Binding so not work. The fields of your form - name = "fields [1]" and name = "fields [0]" are independent from each other, so for each of them your structure should contain its own field:

type FormInfo struct {
    Fields1   string
    Fields2   string
    Action    string
    PageTitle string
    Id        string
}

respectively, in the handler:

...
&f.Fields1: "fields[0]",
&f.Fields2: "fields[1]",
&f.Action:  "action",
...

As a result, the output will be:

(*main.FormInfo)(0xc08200aa50)({
 Fields1: (string) (len=7) "value 1",
 Fields2: (string) (len=7) "value 2",
 Action: (string) (len=4) "save",
 PageTitle: (string) "",
 Id: (string) ""
})

EDIT:

If you change the code in the form on the

...
<input type="text" name="fields"...
<input type="text" name="fields"...

you can get

info.Fields = [value 1 value 2]

without changing its original code.

edited Sep 29, 2015 at 11:59

answered Sep 28, 2015 at 23:59

user4651282

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1 Comment

FlowRaja Over a year ago

What should the form look like if I have to scan into an array? Meaning, I do not want to change the structure of FormInfo, what do I change in template?

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