client.ex

defmodule Client do
  defmacro __using__(resources: resources) do
    for {singlular, plural} <- resources do
      quote bind_quoted: [singlular: singlular, plural: plural] do
        def one(singlular, id) do
          get("/api/#{plural}/#{id}")
        end
      end
    end
  end

  def get(url) do
    IO.puts inspect(url)
  end
end

defmodule AppCode do
  use Client, resources: [{:product, :products}, {:category, :categories}]
  def test, do: Client.one(:product, 12)
end