form_object_example.rb

# config/routes.rb
Rails.application.routes.draw do
  resource :contact_message, only: [:new, :create], path: "/contact", path_names: {new: "/"}
end

# app/controllers/contact_messages_controller.rb
class ContactMessagesController < ApplicationController
  def new
    render locals: {form: ContactMessageForm.new}
  end

  def create
    form = ContactMessageForm.new(contact_message_params)
    
    if form.valid?
      VisitorMailer
        .with(recipient: form, message: form.message)
        .contact_email
        .deliver_later
      
      redirect_to root_path
    else
      render "new", locals: {form: form}
    end
  end

  private

  def contact_message_params
    params
      .require(:form)
      .permit(:name, :email, :phone, :message)
  end
end

# app/forms/contact_message_form.rb
class ContactMessageForm
  include ActiveModel::Model
  attr_accessor :name, :email, :phone, :message

  validates_presence_of :name, :email, :message
  validates :email, email_address: true, allow_nil: true
end

# app/views/contact_messages/new.html.erb
<%= form_for(form, as: :form, url: contact_messages_path) do |f| %>
  …
<% end %>