photo_controller.ex

def create(conn, %{"photo" => %{"image" => image_params} = photo_params}) do
    album_id = photo_params["album_id"]

    ExAws.S3.put_bucket("#{album_id}", "")
      |> ExAws.request()

    Enum.map(image_params, fn(img) ->
      album = album_id
      ext = Path.extname(img.filename)
      u = Ecto.UUID.generate
      flnm = "#{u}#{ext}"

      {:ok, file_binary} = File.read(img.path)

      s3_bucket = album
      {:ok, _} =
        ExAws.S3.put_object(s3_bucket, flnm, file_binary)
        |> ExAws.request()

      store(conn, flnm, album)
    end)
end