Live Form

    <.form for={@form} phx-submit="save_phoenix" multipart
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <.file_upload field={@form[:attachment]} class="file-upload">
    <:label>Attachment</:label>
    <:close>
      <.heroicon name="hero-x-mark" />
    </:close>
    <:error :let={msg}>
      <.heroicon name="hero-exclamation-circle" class="icon" />
      {msg}
    </:error>
  </.file_upload>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</.form>

  

    defmodule MyAppWeb.FileUploadFormLive do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    phoenix_form =
      Phoenix.Component.to_form(%{"attachment" => nil}, as: :file_upload_phoenix, id: "file-upload-live-form-phoenix")

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

  def handle_event("save_phoenix", %{"file_upload_phoenix" => params}, socket) do
{:noreply, socket}
  end
end

  

    <.form for={@form} action={~p"/file-upload/form"} method="post" multipart
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <input type="hidden" name="file_upload_validate[_sent]" value="1" />
  <.file_upload field={@form[:attachment]} class="file-upload">
    <:label>Attachment</:label>
    <:close>
      <.heroicon name="hero-x-mark" />
    </:close>
    <:error :let={msg}>
      <.heroicon name="hero-exclamation-circle" class="icon" />
      {msg}
    </:error>
  </.file_upload>
  <.action type="submit" class="button ui-accent">Submit</.action>
</.form>

  

    defmodule MyAppWeb.FileUploadFormLive do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    ecto_form =
      %MyApp.Form.FileUploadForm{}
      |> MyApp.Form.FileUploadForm.changeset_validate(%{})
      |> Phoenix.Component.to_form(as: :file_upload_ecto, id: "file-upload-live-form-ecto")

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

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

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

  def handle_event("save", %{"file_upload_ecto" => params}, socket) do
    case MyApp.Form.FileUploadForm.changeset_validate(%MyApp.Form.FileUploadForm{}, params) do
      %Ecto.Changeset{valid?: true} = changeset ->
        _data = Ecto.Changeset.apply_changes(changeset)

        {:noreply,
         assign(
           socket,
           :ecto_form,
           Phoenix.Component.to_form(
             MyApp.Form.FileUploadForm.changeset_validate(%MyApp.Form.FileUploadForm{}, params),
             as: :file_upload_ecto,
             id: "file-upload-live-form-ecto"
           )
         )}

      changeset ->
        {:noreply,
         assign(
           socket,
           :ecto_form,
           Phoenix.Component.to_form(changeset,
             action: :insert,
             as: :file_upload_ecto,
             id: "file-upload-live-form-ecto"
           )
         )}
    end
  end
end

  

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

  embedded_schema do
    field :attachment, :map, virtual: true
  end

  def changeset(form, attrs \\ %{}) do
    cast(form, attrs, [:attachment])
  end

  def changeset_validate(form, attrs \\ %{}) do
    form
    |> cast(attrs, [:attachment])
    |> validate_attachment_required()
  end

  defp validate_attachment_required(changeset) do
    upload = get_change(changeset, :attachment)

    if present_upload?(upload) do
      changeset
    else
      add_error(changeset, :attachment, "can't be blank", validation: :required)
    end
  end

  defp present_upload?(%Plug.Upload{filename: name}) when is_binary(name) and name != "", do: true
  defp present_upload?(_), do: false
end