How to create a nested hash through dynamic forms

Question

I am exploring dynamic forms for my app and currently I would like to build a nested hash and currently following Railscasts' ep 403. Thus, the following are my model and form:

Model:

class Product < ActiveRecord::Base
  belongs_to :product_type
  serialize :properties, Hash
end

Form:

<%= f.hidden_field :product_type_id %>

<%= f.fields_for :properties, OpenStruct.new(@product.properties) do |builder| %>
  <% @product.product_type.fields.each do |field| %>
    <%= render "products/fields/#{field.field_type}", field: field, f: builder %>
  <% end %>
<% end %>

The output I am getting is:

"properties"=>{"Name"=>"Great Prod", "Remarks"=>"Super!", "Year"=>"2015"}

Data structure view:

- properties
 -- Name: "Great Prod"
 -- Remarks: "Super!"
 -- Year: "2015"

What I am looking for is:

"properties"=>{"2015"=>{"Name"=>"Great Prod", "Remarks"=>"Super!"}}

Data structure view:

- properties
 -- "2015"
   --- Name: "Great Prod"
   --- Remarks: "Super!"

How do I go about the above to achieve it? Thank you!

Edit 1: Corrected the expected hash for the above and added simple data structure view.

Answer 1

So instead of using hash for year, I actually created a new model for year and from there, store each properties as hash.