Overriding list impl?

[cjbottaro]

Hi. I'd like to override the list encoder to be able to handle keyword lists. Something like this:

defimpl Poison.Encoder, for: List do
  def encode(list, options) do
    if Keyword.keyword?(list) do
      list |> Map.new |> super
    else
      super(list)
    end
  end
end

Is that possible? If so, how? Thanks!

[anthonylebrun]

This seems like a more generic question about Elixir protocols rather than Poison, but I'm also trying to find the answer to that. What's the idiomatic way to handle this? Do you have to understand the Any implementation of encode and re-implement the default behavior yourself?

[mlankenau]

We are overwriting existing modules like:

defimpl Poison.Encoder, for: [Ecto.Date, Ecto.Time, Ecto.DateTime] do
  def encode(dt, _opts), do: <<?", @for.to_iso8601(dt)::binary, ?">>
end

The only problem are the warnings:

warning: redefining module Poison.Encoder.Ecto.Date (current version loaded from _build/test/lib/ecto/ebin/Elixir.Poison.Encoder.Ecto.Date.beam)                                                          
  lib/poison.ex:5

If someone knows how to do it without warnings...