Live Form

    <.form for={@form} phx-submit="save_phoenix"
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <.pin_input field={@form[:pin]} count={4} class="pin-input">
    <:label>Code</:label>
  </.pin_input>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</.form>

  

    defmodule MyAppWeb.PinInputFormLive do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    phoenix_form =
      Phoenix.Component.to_form(%{"pin" => []}, as: :pin_phoenix, id: "pin-input-live-form-phoenix")

    {:ok, assign(socket, :phoenix_form, phoenix_form)}
  end

  def handle_event("save_phoenix", %{"pin_phoenix" => params}, socket) do
    pin = List.wrap(params["pin"])

    {:noreply,
     assign(
       socket,
       :phoenix_form,
       Phoenix.Component.to_form(%{"pin" => pin}, as: :pin_phoenix, id: "pin-input-live-form-phoenix")
     )}
  end

  def handle_event("save_phoenix", _params, socket) do
    {:noreply, socket}
  end
end

  

    <.form for={@form} phx-change="validate" phx-submit="save"
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <.pin_input field={@form[:pin]} count={4} class="pin-input">
    <:label>Code</:label>
    <:error :let={msg}>
      <.heroicon name="hero-exclamation-circle" class="icon" />
      {msg}
    </:error>
  </.pin_input>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</.form>

  

    defmodule MyAppWeb.PinInputFormLive do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    ecto_form =
      %MyApp.Form.PinInputForm{}
      |> MyApp.Form.PinInputForm.changeset_validate(%{})
      |> Phoenix.Component.to_form(as: :pin_ecto, id: "pin-input-live-form-ecto")

    {:ok, assign(socket, :ecto_form, ecto_form)}
  end

  def handle_event("validate", %{"pin_ecto" => params}, socket) do
    changeset =
      %MyApp.Form.PinInputForm{}
      |> MyApp.Form.PinInputForm.changeset_validate(params)
      |> Map.put(:action, :validate)

    {:noreply,
     assign(
       socket,
       :ecto_form,
       Phoenix.Component.to_form(changeset,
         action: :validate,
         as: :pin_ecto,
         id: "pin-input-live-form-ecto"
       )
     )}
  end

  def handle_event("save", %{"pin_ecto" => params}, socket) do
    case MyApp.Form.PinInputForm.changeset_validate(%MyApp.Form.PinInputForm{}, params) do
      %Ecto.Changeset{valid?: true} = changeset ->
        {:noreply,
         assign(
           socket,
           :ecto_form,
           Phoenix.Component.to_form(
             MyApp.Form.PinInputForm.changeset_validate(%MyApp.Form.PinInputForm{}, params),
             as: :pin_ecto,
             id: "pin-input-live-form-ecto"
           )
         )}

      changeset ->
        {:noreply,
         assign(
           socket,
           :ecto_form,
           Phoenix.Component.to_form(changeset,
             action: :validate,
             as: :pin_ecto,
             id: "pin-input-live-form-ecto"
           )
         )}
    end
  end

  def handle_event("save", _params, socket) do
    {:noreply, socket}
  end
end

  

    defmodule MyApp.Form.PinInputForm do
  use Ecto.Schema
  import Ecto.Changeset

  embedded_schema do
    field :pin, {:array, :string}
  end

  def changeset_validate(form, attrs \\ %{}) do
    form
    |> cast(attrs, [:pin])
    |> validate_required([:pin], message: "can't be blank")
    |> validate_length(:pin, is: 4, message: "must be 4 digits")
  end
end