Getting dynamic array from golang Post Form

Question

I am currently working in Golang, I am developing an API, in a POST handler I need to receive in the Post form an array but with named positions, I mean, something like this:

myarray[a]:"some Value"
myarray[otherName]: "some Other value"
myarray[x] : "something different"

Right now I am trying making the Post request using curl in the CLI. I am sending this:

curl -i -X POST --url http://localhost:20000/myendpoint -H "Content-Type: application/x-www-form-urlencoded" -d 'Name=Comp&myarray[x]=somethingdifferent&myarray[otherName]=someOtherValue'

And, indeed when I print the form values in Go, I get:

[myarray[x]:[somethingdifferent] myarray[otherName]:[someOtherValue]]

Until here I understand everything, then I need to get the array myarray in a golang variable, how can I do this? When I do:

req.Form["myarray"]

I get nothing there, my purpose is to get that array and store it as a JSON object in the database due that I don't know which field can be sent in that array. I need something like:

myarray[[x]=somethingdifferent,[otherName]=someOtherValue]

That's not HTTP query parameters work, you have 2 separate variables called "myarray[x]" and "myarray[otherName]". Are you trying to parse those into a map? — Mr_Pink
– Mr_Pink, Commented Oct 6, 2017 at 15:02
@JimB correct, right now I am getting them as two separate variables, but I need them in some way in one array so then I can convert it to json and save it — Sredny M Casanova
– Sredny M Casanova, Commented Oct 6, 2017 at 15:06
There's no shortcut here, you need to parse those strings and assign them to a map. A json array can't have string indices, so you can use a slice (and you don't want an array in Go). — Mr_Pink
– Mr_Pink, Commented Oct 6, 2017 at 15:20
Seems like there's a general confusion in this question about the difference between an array and a map/hash/dictionary. — Adrian
– Adrian, Commented Oct 6, 2017 at 15:29
Sorry to add to the confusion, that should be "you can't use a slice". — Mr_Pink
– Mr_Pink, Commented Oct 6, 2017 at 15:35

Eugene Lisitsky · Accepted Answer · 2017-10-07 06:57:12Z

You may parse it yourself:

func extractDynArray(form url.Values, key string) (result map[string]interface{}, err error) {
    result = make(map[string]interface{})
    reg, err := regexp.Compile(`^([a-z]+)\[([a-z]+)\]$`)
    if err != nil {
        log.Fatalf("Error compiling regexp: %v", err)
    }
    var matches [][]string
    for k, v := range form {
        matches = reg.FindAllStringSubmatch(k, -1)
        if len(matches) != 1 {
            continue
        }
        if key != "" && matches[0][1] != key {
            continue
        }
        if len(matches[0]) != 3 {
            continue
        }
        result[matches[0][2]] = v
    }
    return
}

func handler(w http.ResponseWriter, r *http.Request) {
    err := r.ParseForm()
    if err != nil {
        log.Fatalf("Cannot parse form %v", err)
    }
    //form := r.Form["myarray"]
    fmt.Printf("Form: %+v\n", r.Form)
    fmt.Printf("Form myarray: %+v \n", r.Form["myarray"])
    parsed, err := extractDynArray(r.Form, "myarray")
    fmt.Printf("Parsed: %v. Err: %v", parsed, err)
}

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