Another way to clean up this code without changing any semantics of how it works would be to use guard clauses:
defp parse_attr(attr, value) when attr in [:title, :author, :description],
do: String.trim(value)
defp parse_attr(:body, value),
do: value
defp parse_attr(:tags, value),
do: value |> String.split(",") |> Enum.map(&String.trim/1) |> Enum.sort()
This keeps the functionality intact where this function will reject if not called with one of the specific atoms defined in the function head, but it’s slightly less code to write for each case.
Edit: did not originally see the second part of @srowley’s example, they suggested this approach as well. Anyway, this is how I’d do it.
