Ecto find_or_create_by

defmodule EctoTest.Repo do
  use Ecto.Repo, otp_app: :ecto_test

  import Ecto.Query

  def find_or_create_by(queryable, attrs) do
    q = Enum.reduce(attrs, queryable, fn
      {field, val}, query ->
        query |> where([x], field(x, ^field) == ^val)
        _, query -> query
    end)

    r = all(q)

    if r == [] do
      insert!(struct(queryable, attrs))
    else
      hd(r)
    end
  end

end