nested attributes with dynamic form

contact.rb

class Contact < ActiveRecord::Base
  has_many :responses
  has_many :dynaforms, through: :responses

  attr_accessible :email, :responses_attributes
  
  accepts_nested_attributes_for :responses

  def self.new_with_dynaforms
    new.tap do |contact|
      Dynaform.all.each do |dynaform|
        contact.responses.build dynaform: dynaform, dynaform_name: dynaform.form_name, dynaform_type: dynaform.form_type
      end
    end
  end
end

dynafom.rb

class Dynaform < ActiveRecord::Base
  has_many :responses
  has_many :contacts, through: :responses
  
  attr_accessible :form_type, :form_name
end

index.html.erb

<% @contacts.each do |contact| %>
<div>
  <strong><%= contact.email %></strong><br />
  <% contact.responses.each do |response| %>
    <%= response.form_name %> : <%= response.value %><br />
  <% end %>
</div>
<% end %>

new.html.erb

<%= form_for @contact, url: responses_path do |f| %>
<div>
  <%= f.label :email %>
  <%= f.text_field :email %>
</div>

  <%= f.fields_for :responses do |response_fields| %>
  <div>
    <%= response_fields.label :value, response_fields.object.dynaform_name %>
    <%= response_fields.send(response_fields.object.dynaform_type, :value) %>
    <%= response_fields.hidden_field :dynaform_id %>
  </div>
  <% end %>

  <%= f.submit %>
<% end %>

response.rb

class Response < ActiveRecord::Base
  belongs_to :contact
  belongs_to :dynaform

  attr_protected :contact_id

  validates_presence_of :dynaform

  attr_accessor :dynaform_name, :dynaform_type

  def dynaform_name
    dynaform.try(:form_name)
  end

  def dynaform_type
    dynaform.try(:form_type)
  end
end

responses_controller.rb

class ResponsesController < ApplicationController
  def index
    @contacts = Contact.all(:include => :attributes)
  end

  def new
    @contact = Contact.new_with_dynaforms
  end

  def create
    @contact = Contact.new params[:contact]

    if @contact.save
      redirect_to responses_url
    else
      render action: :new
    end
  end
end