coordinator.ex

defmodule Metex.Coordinator do

  def loop(results \\ [], results_expected) do
    receive do
      {:ok, result} ->
        new_results = [result|results]
        if results_expected == Enum.count(new_results) do
          send self, :exit
        end
        loop(new_results, results_expected)
        :exit -> IO.puts(results |> Enum.sort |> Enum.join(", "))
        _ -> loop(results, results_expected)
    end
  end

end

metex.ex

defmodule Metex do
  def temperatures_of(cities) do
    coordinator_pid =
      spawn(Metex.Coordinator, :loop,[[], Enum.count(cities)])

      cities |> Enum.each(fn city ->
        worker_pid = spawn(Metex.Worker, :loop,[])
        send worker_pid, {coordinator_pid, city}
      end)
  end
end

worker.ex

defmodule Metex.Worker do

  def loop do
    receive do
        {sender_pid, location} -> send(sender_pid, {:ok, temperature_of(location)})
        _ -> IO.puts "don't know how to process this message"
    end
    loop
  end
  
  #new task
  
    def loadbytasks(location) do
    bb = Task.async(fn ->
      hipi(location)
    end)
    Task.await bb
  end

  def hipi(cities) do
    cities |> Enum.map(fn cities -> temperature_of(cities)end)
  end
  
  
  defp temperature_of(location) do

    result = url_for(location) |> HTTPoison.get |> parse_response

    case result do
      {:ok, temp} -> "#{location} : #{temp} °C"
      :error -> "#{location} not found"
    end

  end

  defp url_for(location) do
    location = URI.encode(location)
    "http://api.openweathermap.org/data/2.5/weather?q=#{location}&appid=#{apikey()}"
  end

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

  defp parse_response(_) do
    :error
  end

  defp computer_temperature(json) do
    try do
      temp = (json["main"]["temp"] - 273.15) |> Float.round(1)
      {:ok, temp}
    rescue
      _ -> :error
    end
  end

  defp apikey do
    "af206b25b0f2be7c78df109d02a2bb68"
  end
end