Reform on Rails

Models:

class Person
  include ActiveModel::Model
  attr_accessor :name, :pet
end

class Pet
  include ActiveModel::Model
  attr_accessor :name, :kind
end

Forms:

class PetForm < Reform::Form
  property :name
  property :kind
end

class PersonsForm < Reform::Form


  property :name
  
  #nested form with do..end block
=begin
  property :pet do
    property :name
    property :kind
  end
=end
  # nested form with form option
  property :pet, form:PetForm
end

ERB tpl:
<!-- main form -->
<%= form_for(@persons_from, as: :person, url: '/dashboard/person', method: "put") do |form| %>
    <%= form.text_field :name, autofocus: true, placeholder:"Person Name", class:"rui-input" %>
    <!-- nested form -->
    <%= form.fields_for :pet, @persons_from.pet do |sub_form| %>
        <%= sub_form.text_field :name, autofocus: false, placeholder:"Pet Name", class:"rui-input" %>
        <%= sub_form.text_field :kind, autofocus: false, placeholder:"Pet Kind", class:"rui-input" %>
    <% end %>
    <%= submit_tag("Submit", :class => "rui-button-brand rui-mobile-block", :id => "submit") %>
<% end %>