Required validation still failing after put_assoc

Jump off point, same problem, but this solution isn’t working for me.

I have a many_to_many association. Even after getting put_assoc right, the error field for that many to many is still there.

This is the IO.inspect result of the changeset

#Ecto.Changeset<
  action: nil,
  changes: %{
    event_id: 1,
    languages: [
      #Ecto.Changeset<
        action: :insert,
        changes: %{id: 1, value: "Cree"},
        errors: [],
        data: #DeAboriginal.Data.Language<>,
        valid?: true
      >,
      #Ecto.Changeset<
        action: :insert,
        changes: %{id: 2, value: "Algonquin"},
        errors: [],
        data: #DeAboriginal.Data.Language<>,
        valid?: true
      >,
      #Ecto.Changeset<
        action: :insert,
        changes: %{id: 3, value: "Miqmaq"},
        errors: [],
        data: #DeAboriginal.Data.Language<>,
        valid?: true
      >,
      #Ecto.Changeset<
        action: :insert,
        changes: %{id: 4, value: "Ojibwe"},
        errors: [],
        data: #DeAboriginal.Data.Language<>,
        valid?: true
      >
    ],
    name: "edede"
  },
  errors: [
    languages: {"is invalid", [validation: :assoc, type: {:array, :map}]}
  ],
  data: #DeAboriginal.Data.Activity<>,
  valid?: false
>

This is the function that generates the above inspect

  def create_activity(attrs \\ %{}) do
    language_map = Enum.map(attrs["languages"],
                          fn x -> x
                                  |> get_language!()
                                  |> fn y -> %{id: y.id, value: y.value} end.()
                          end)

    %Activity{}
    |> Activity.changeset(attrs)
    |> Ecto.Changeset.put_assoc(:languages, language_map)
    |> IO.inspect()
    |> Repo.insert()
    end

And this is the function upstream of the that, which is the :create

  def create(conn, %{
    "activity" => activity,
    "application_id" => application_id,
    "event_id" => event_id,
  }) do

    case Data.create_activity(activity) do
      {:ok, struct} -> conn
       |> put_flash(:info, "#{struct.name} created!")
       |> redirect(to: Routes.application_event_activity_path(conn, :new, application_id, event_id))
    end
  end

This is the :new

  def new(conn, %{
    "application_id" => app_id,
    "event_id" => event_id
  }) do

    changeset = Data.Activity.changeset(%Data.Activity{
      languages: []
    }, %{})

    languages = Data.list_language()
    render(conn, "new.html",
      activity: changeset,
      application_id: app_id,
      event_id: event_id,
      languages: languages
      )
  end

Also is there a comprehensive Ecto guide out there specific with dealing with the relationships? I feel this association stuff all over the place and everyone that writes about it have their own way of working around it.