Controller Form

    <.form
  for={@form}
  action={~p"/tags-input/form"}
  method="post"
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <.tags_input field={@form[:tags]} class="tags-input">
    <:label>Keywords</:label>
    <:close><.heroicon name="hero-x-mark" /></:close>
    <:error :let={msg}>
      <.heroicon name="hero-exclamation-circle" class="icon" />
      {msg}
    </:error>
  </.tags_input>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</.form>

  

    def tags_input_form_page(conn, _params) do
  phoenix_form =
    Phoenix.Component.to_form(%{"tags" => ["alpha", "beta"]}, as: :tags_input_phoenix, id: "tags-input-form-phoenix")

  render(conn, :tags_input_form_page, phoenix_form: phoenix_form)
end

def tags_input_form_submit(conn, params) do
  if is_map(params["tags_input_phoenix"]) do
    tags = params["tags_input_phoenix"]["tags"] || ""

    conn
    |> put_flash(:info, "Submitted: tags=#{inspect(tags)}")
    |> redirect(to: ~p"/tags-input/form#tags-input-form-phoenix")
  end
end

  

    <.form
  for={@form}
  action={~p"/tags-input/form"}
  method="post"
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <input type="hidden" name="_csrf_token" value={Plug.CSRFProtection.get_csrf_token()} />
  <.tags_input field={@form[:tags]} class="tags-input">
    <:label>Keywords</:label>
    <:close><.heroicon name="hero-x-mark" /></:close>
    <:error :let={msg}>
      <.heroicon name="hero-exclamation-circle" />
      {msg}
    </:error>
  </.tags_input>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</.form>

  

    def tags_input_form_page(conn, _params) do
  form =
    MyApp.Forms.TagsInputForm.changeset_validate(%MyApp.Forms.TagsInputForm{}, %{"tags" => ["alpha", "beta"]})
    |> Phoenix.Component.to_form(as: :tags_input_changeset, id: "tags-input-changeset-form")

  render(conn, :tags_input_form_page, form: form)
end

def tags_input_form_create(conn, %{"tags_input_changeset" => params}) do
  case MyApp.Forms.TagsInputForm.changeset_validate(%MyApp.Forms.TagsInputForm{}, params) do
    %Ecto.Changeset{valid?: true} = changeset ->
      data = Ecto.Changeset.apply_changes(changeset)
      conn
      |> put_flash(:info, "Submitted: tags=#{data.tags}")
      |> redirect(to: ~p"/tags-input/form#tags-input-changeset-form")

    changeset ->
      changeset = Map.put(changeset, :action, :insert)

      form =
        Phoenix.Component.to_form(changeset,
          as: :tags_input_changeset,
          id: "tags-input-changeset-form"
        )

      render(conn, :tags_input_form_page, form: form)
  end
end

  

    defmodule MyApp.Forms.TagsInputForm do
  use Ecto.Schema
  import Ecto.Changeset

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

  def changeset(form, attrs \\ %{}) do
    form
    |> cast(attrs, [:tags])
    |> validate_required([:tags])
    |> validate_tag_count(:tags, 3)
  end

  def changeset_validate(form, attrs \\ %{}) do
    form
    |> cast(attrs, [:tags])
    |> validate_required([:tags], message: "can't be blank")
    |> validate_tag_list(:tags, 3)
  end

  defp validate_tag_count(changeset, field, max) do
    validate_change(changeset, field, fn _, value ->
      n = if is_list(value), do: length(value), else: 0
      if n <= max, do: [], else: [{field, "must have at most #{max} tags"}]
    end)
  end

  defp validate_tag_list(changeset, field, max) do
    validate_change(changeset, field, fn _, value ->
      cond do
        not is_list(value) -> [{field, "is invalid"}]
        length(value) > max -> [{field, "must have at most #{max} tags"}]
        Enum.any?(value, &String.contains?(&1, ";")) -> [{field, "must not contain semicolons"}]
        true -> []
      end
    end)
  end
end

  

    <form
  action={~p"/tags-input/form"}
  method="post"
  class="flex flex-col gap-space-lg w-full max-w-xl"
>
  <input type="hidden" name="_csrf_token" value={Plug.CSRFProtection.get_csrf_token()} />
  <.tags_input
    name="tags_native[tags]"
    class="tags-input"
    value={["alpha", "beta"]}
  >
    <:label>Keywords</:label>
    <:close><.heroicon name="hero-x-mark" /></:close>
  </.tags_input>
  <.action type="submit" class="button ui-accent">
    Submit
  </.action>
</form>

  

    def tags_input_form_submit(conn, %{"tags_native" => %{"tags" => tags}}) do
  conn
  |> put_flash(:info, "Submitted: tags=#{inspect(tags)}")
  |> redirect(to: ~p"/tags-input/form#tags-input-form-native")
end