Remove square brackets [] from POST method

I am using elixir - phoenix - tesla - third party api

I want to send a post request to the third party api and send the same parameter with two different values, which in the third party api documentation stated that it is possible to do it. but i want to remove the square brackets around the parameter.

Currentley I get this is what is being sent:


the api sends a response that Parameter 'shades' is missing

i want it like this:


this is my code using Tesla — tesla v1.4.4

    {:ok, response} = request(method: :post, url: "/edit", body: [green: "yes", blue: "no", shades: [List.first(shades), List.last(shades)]])

it works when sending one parameter in a map like this:

      "green" => "yes,
      "blue" => "no",
      "shades" => 300

but again I need to send two values at the same time, how do I achieve this?

It looks like you may have configured Tesla to use Plug.Conn.Query to encode the params, and it looks like it throws away repeat params, which is how I would have expected to get your thing to work.

I think what I would look at would be passing your own :encode option to Tesla.Middleware.FormUrlencoded that allows duplicates.

1 Like

you are absolutley right! I am using

  encode: &Plug.Conn.Query.encode/1,
  decode: &Plug.Conn.Query.decode/1)

thank you for this information

I want to admit that I am pretty new to elixir but after digging a little bit I managed to get it to work using this:

Plug Repository

  # covers non-keyword lists
  defp encode_pair(parent_field, list, encoder) when is_list(list) do
    mapper = fn
      value when is_map(value) and map_size(value) != 1 ->
        raise ArgumentError,
              "cannot encode maps inside lists when the map has 0 or more than 1 element, " <>
                "got: #{inspect(value)}"

      value ->
        [?&, encode_pair(parent_field <> "", value, encoder)]

    |> Enum.flat_map(mapper)
    |> prune()

instead of [?&, encode_pair(parent_field <> "[]", value, encoder)] in last line, i just removed the [] like this: [?&, encode_pair(parent_field <> "", value, encoder)]

what I want to know if this is the right way to do it? and would this cause any issues noting that I am only going to be using it for this API call?