Do you maintain both @data and @form that is based on @data as the "source of truth"?

[nallwhy]

I do that like below.

@impl true
def handle_event("event", %{"data" => data}, socket) do
  your_params = %{...}

  data_params =
    socket.assigns.form.source.params
    |> Map.merge(your_params)

  form =
    DataParams.changeset(%DataParams{}, data_params)
    |> to_form(as: :data)
    |> Map.put(:action, :validate)

  socket = socket |> assigns(:form, form)

  {:noreply, socket}
end

To make it easily, I made a simple helper library.

Doumi.Phoenix.Params - A helper library that supports converting form to params and params to form

Doumi.Phoenix.Params is a helper library that supports converting form to params and params to form. It is still confusing to handle Ecto.Changeset, Phoenix.HTML.Form for form binding. For example, To make it easy and straightforward, I’ve made Doumi.Phoenix.Params. defmodule MyAppWeb.TestParams do use Ecto.Schema import Ecto.Changeset @primary_key false embedded_schema do field :foo, :string end @required [:foo] def changeset(%__MODULE__{} = struct, attrs) do struct…