def deps do
  [{:formex_vex, "~> 0.1.0"}]
end

config :formex,
  validator: Formex.Validator.Vex

  def build_form(form) do
    form
    |> add(:name, :text_input, validation: [presence: :true, length: [in: 10..150]])
    |> add(:content, :textarea, validation: [presence: [message: "can't be blank"]])
    |> add(:slug, :text_input, validation: fn (text) ->
      if !Repo.get_by(Article, slug: text) do
        :ok
      else
        {:error, "already used!!1"}
      end
    end)
    # ...
  end