Encoding map to JSON using Poison for use with Slack
<p>I'm using Poison to encode a map to JSON that will send it to the Slack API. This is what Poison gives me:</p>

<pre><code>"{\"text\":\"changed readme fad996e98e04fd4a861840d92bdcbbcb1e1ec296\"}"
</code></pre>

<p>When I put that into JSON lint it says it is valid JSON, but Slack responds "invalid payload".</p>

<p>If I change the JSON to look like this</p>

<pre><code>{"text":"changed readme fad996e98e04fd4a861840d92bdcbbcb1e1ec296"}
</code></pre>

<p>Then it works. Does anyone know where I'm going wrong with this? Do I need to do extra processing on the encoded JSON or is there some header I need to set?</p>

<p>Here is my controller</p>

<pre><code>def create(conn, opts) do
    message = Message.create_struct(opts)
    response = Slack.Messages.send(message)

    case response do
      {:ok, data} -&gt;
        render conn, json: Poison.encode!(data)
      {:error, reason} -&gt;
        render conn, json: reason
    end
end
</code></pre>

<p>Here is part of the library for sending the messages</p>

<pre><code>defmodule Slack.Messages do

  def format_simple_message(map) do
    text = map.description &lt;&gt; " " &lt;&gt; map.commits
    message = %{text: text}
  end

  def post_to_slack(map) do
    Slack.post(:empty, map)
  end

  def send(map) do
    map
    |&gt; format_simple_message
    |&gt; post_to_slack
  end

end
</code></pre>

<p>And my HTTPoison processing</p>

<pre><code>defmodule Slack do
  use HTTPoison.Base

  @endpoint "http://url.com"

  def process_url() do
    @endpoint
  end

  def process_response_body(body) do
    body
    |&gt; Poison.decode! # Turns JSON into map
  end

  def process_request_body(body) do
    body
    |&gt; Poison.encode! # Turns map into JSON
  end
end
</code></pre>

<p>The part that creates the JSON is in the last block.</p>