Golang parse form

Question

If I have the following form setup:

{{ range $key, $value := .Scores }}
    <input id="{{$value.Id}}_rating__1" type="radio" name="rating[{{$value.Id}}]" value="-1">
    <input id="{{$value.Id}}_rating__0" type="radio" name="rating[{{$value.Id}}]" value="0">
    <input id="{{$value.Id}}_rating__2" type="radio" name="rating[{{$value.Id}}]" value="+1">
{{ end }}

How can I then extract that data correctly? Knowing that there .Scores can contain multiple structs

func categoryViewSubmit(w http.ResponseWriter, r *http.Request) {
    err := r.ParseForm()
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("POST")

    fmt.Printf("%+v\n", r.Form()) // annot call non-function r.Form (type url.Values)
    fmt.Printf("%+v\n", r.FormValue("rating")) // Returns nothing
}

score 16 · Accepted Answer · 2015-02-01 05:25:57Z

16

The form keys look like rating[id] where id is a value identifier. To get one of the values, call r.FormValue("rating[id]") after substituting id for an actual id value.

I suggest printing the form to see what's going on:

fmt.Printf("%+v\n", r.Form)  // No () following Form, Form is not a function

The form is an url.Values. An url.Values is a map[string][]string. You can iterate through the form as follows:

for key, values := range r.Form {   // range over map
  for _, value := range values {    // range over []string
     fmt.Println(key, value)
  }
}

edited Feb 1, 2015 at 5:25

answered Feb 1, 2015 at 4:53

user5728991

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1 Comment

woutr_be Over a year ago

Thanks for this, just one question, is there a way to iterate through that map? I will never know the different ids, so I can't substitute it. The only way would be to iterate over all the form data, and grab the id from there.

Henri · Accepted Answer · 2016-02-25 06:29:34Z

For others that are looking answers for this I found Gorilla's schema really helpful. It allows you to parse forms to structs and has support for arrays and nested structs. When you combine that with guregu's null package you can easily parse sructs with optional fields.

Example Go:

package models

import (
    "github.com/gorilla/schema"
    "gopkg.in/guregu/null.v3"
)

type User struct {
    Id            null.Int    `db:"id" json:"id"`
    // Custom mapping for form input "user_name" 
    Name          string      `db:"user_name" json:"user_name" schema:"user_name"`
    EmailAddress  string      `db:"email_address" json:"email_address"`
    OptionalField null.String `db:"optional_field" json:"optional_field"`
}

Example html

<form>
    <input type="text" name="user_name">
    <input type="text" name="EmailAddress">
    <input type="text" name="OptionalField">
</form>

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