Convert elixir map to query string

map_to_query_string.ex

defmodule URL do
  def to_query(input, namespace) do
    Enum.map(input, fn({key, value}) -> parse("#{namespace}[#{key}]",value)end) 
    |> Enum.join("&")
  end

  def to_query(input) do
    Enum.map(input, fn({key, value}) -> parse(key,value) end)
    |> Enum.join("&")
  end

  def parse(key, value) when is_map(value) do
    to_query(value, key)
  end

  def parse(key, value) do: 
    "#{key}=#{value}"
  end
end

Came here looking for a more elegant solution to what I felt wasn't very 'functional'.

@endpoint "https://domain.tld"
options_list = Map.to_list(options)
options_formatted = ""

for {key, value} <- options_list do
  options_formatted <> "?" <> Atom.to_string(key) <> "=" <> value <> "&"
end

@endpoint <> options_formatted

The to_query function is especially neat! Thanks for the inspiration.

I think https://hexdocs.pm/elixir/URI.html#encode_query/1 would be the first thing to try

Convert Query String Parameters into a Map of Key/Value Pairs:

iex(29)> String.split("from=ME&to=YOU&to_index=THERE&proof=PROVEN", ~r/&|=/) |> Enum.chunk(2) |> Map.new(fn [k, v] -> {k, v} end)
%{"from" => "ME", "proof" => "PROVEN", "to" => "YOU", "to_index" => "THERE"}

https://gist.github.com/ltfschoen/a52109ea5a9e020fa4abcaacbc43e8af