Protocol String.Chars not implemented for

sriki

I got the error mentioned in the title while running the following code. The weird part is I did get the response I expected but with this message attached.

defmodule Kodi.Worker do
def get_response() do
    result = url_for() |> HTTPoison.get |> parse_response
    case result do
        {:ok, response} -> "response: #{response}"
        :error -> "query error"
    end
end

defp url_for() do
    "http://192.168.0.104:8080/jsonrpc?request={%22jsonrpc%22:%20%222.0%22,%20%22id%22:%201,%20%22method%22:%20%22Playlist.GetPlaylists%22}"
end

defp parse_response({:ok, %HTTPoison.Response{body: body, status_code: 200}}) do
    body |> JSON.decode! |> filter_response
end

defp parse_response(_) do
    :error
end

defp filter_response(json) do
    try do
        #response = (json["result"])
        #{:ok, response}
        {:ok, json}
    rescue
        _ -> :error
    end
end
end

Any idea?

EDIT:
Error message:
** (Protocol.UndefinedError) protocol String.Chars not implemented for %HTTPoison.Response{body: “{"id":1,"jsonrpc":"2.0","result":[{"playlistid":0,"type":"audio"},{"playlistid":1,"type":"video"},{"playlistid":2,"type":"picture"}]}”, headers: [{“Content-Length”, “133”}, {“Content-Type”, “application/json”}, {“Date”, “Wed, 04 May 2016 05:00:55 GMT”}], status_code: 200}
(elixir) lib/string/chars.ex:3: String.Chars.impl_for!/1
(elixir) lib/string/chars.ex:17: String.Chars.to_string/1
(kodi) lib/worker.ex:5: Kodi.Worker.get_response/0

It looks like you are correct. I might be treating the response as string when it’s not. I will look into it again to figure out how to fix it. Thanks.

I made a mistake in my code. I am fixing it and update the thread “soon”.

8 comments

#protocols #troubleshooting

1 31823 8

2023-10-30 18:38:46 UTC

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NobbZ

It would have been much easier if you had posted the full errormessage including the module for that String.Chars is not implemented and the line number it is complaining about.

So I have to guess for now where the message does come from, and the sole possbility I do see for now is this line: {:ok, response} -> "response: #{response}". response is of type HTTPotion.Response or HTTPotion..AsyncResponse and after a quick look up in the sources I wasn’t able to find a defimpl for both of them and they don’t seem to have Inspect implemented either (there was not a single defimpl in the repository according to github search).

So If that is really the line causing you trouble, You need to get the information you want to have in the string in another way.

Post #1

hubertlepicki

You are not getting this error caused by the code above.

What may be happening is that you are getting a JSON response out from the get_response() function, and later on treat it as a string, while it is Map.

I usually get this error message when I try to use IO.puts instead of IO.inspect to print something out to console that is not a string.

Fuller code example would be better, along with full error message (you cut it off in most interesting part, before the module name).

Post #2

sriki

I missed the “!” in the above line. With that added, I still got an error message but it’s more about the json data structure and how it’s being parsed. I will deal with it. Thanks for pointing in the right direction and apologies for cutting off the full error message.

Post #3