elixir map with mixed keys

in the Phoenix application, I have a function that takes two maps, and creates two entries in the database via Ecto.Changeset.

def create_user_with_data(user_attrs, data_attrs) do
    name = cond do
        data_attrs["name"] ->
            data_attrs["name"]
        data_attrs[:name] ->
            data_attrs[:name]
        true -> nil
    end
    Ecto.Multi.new()
    |> Ecto.Multi.insert(:user, User.registration_changeset(%User{}, Map.put(user_attrs, :name, name)))
    |> Ecto.Multi.run(:user_data, fn(%{user: user}) ->
        %MyApp.Account.UserData{}
        |> MyApp.Account.UserData.changeset(Map.put(data_attrs, :user_id, user.id))
        |> Repo.insert()
    end)
    |> Repo.transaction()
end

because the keys in these map can be both atoms and lines, I have to check these keys.

but the expression

Map.put(user_attrs, :name, name)

will cause an error

** (Ecto.CastError) expected params to be a map with atoms or string keys, got a map with mixed keys: %{:name => "John", "email" => "m@gmail.com"}

if the keys are strings.

Is there any best practice in dealing with this issue?

Solution

I'd convert all the keys to atoms first and then use atoms everywhere.

def key_to_atom(map) do
  Enum.reduce(map, %{}, fn
    {key, value}, acc when is_atom(key) -> Map.put(acc, key, value)
    # String.to_existing_atom saves us from overloading the VM by
    # creating too many atoms. It'll always succeed because all the fields
    # in the database already exist as atoms at runtime.
    {key, value}, acc when is_binary(key) -> Map.put(acc, String.to_existing_atom(key), value)
  end)
end

Then, convert pass all such maps through this function:

user_attrs = user_attrs |> key_to_atom
data_attrs = data_attrs |> key_to_atom

Now you can Map.put atom keys whenever you want to.