_form2.html.erb

<%= nested_form_for @product, html: {class: "form", role: "form"} do |f| %>

<div class="from-group">
	<%= f.label :name, "New Product", class: "" -%>
  <%= f.text_field :name,
			class: "form-control",
			placeholder: "Product Name" -%>
</div>

<%= f.label :details -%>
<%= f.fields_for :details do |d| -%>
<div class="form-group">
	<div class="row">
		<div class="col-sm-2">
			<%= d.label :name %>
			<%= d.text_field :name, class: "form-control", width: "" -%>
		</div>

		<div class="col-sm-2">
			<%= d.label :required_at, "Required" -%>
			<%= d.select(:required_at, [
				["", ""],
				['App', 0],
				['Red', 1],
				['Amber', 2],
				['Green', 3]
			],
			{},
			{class: "form-control"}
			)-%>
		</div>

		<div class="col-sm-1">
      <label>&nbsp;</label>
      <%= d.link_to_remove class: "form-control btn btn-sm btn-danger",
          title: "Remove Ingredient"  do -%>
        <span class="glyphicon glyphicon-remove"></span>
      <% end %>
    </div>
	</div>
</div>
	<%= d.label :properties %>
	<%= d.fields_for :properties, @detail do |p| -%>
<div class="form-group">
	<div class="row">
		<div class="col-sm-3">
		<%= p.label :name %>
		<%= p.text_field :name, class: "form-control", width: "" -%>
		</div>

		    <div class="col-sm-1">
      <label>&nbsp;</label>
      <%= p.link_to_remove class: "form-control btn btn-sm btn-danger",
          title: "Remove Ingredient"  do %>
        <span class="glyphicon glyphicon-remove"></span>
      <% end %>
    </div>
	</div>
</div>
	<% end -%>
<div class="form-group">
  <%= d.link_to_add :properties,
      class: "btn btn-sm btn-info" do %>
    <i class="glyphicon glyphicon-plus"></i>
    Add Property
  <% end %>
</div>

<% end -%>

<div class="form-group">
  <%= f.link_to_add :details,
      class: "btn btn-sm btn-info" do %>
    <i class="glyphicon glyphicon-plus"></i>
    Add Detail
  <% end %>
</div>






<%= f.submit "Create Product",
    class: "btn btn-success" %>





<% end -%>

detail.rb

class Detail < ActiveRecord::Base
	belongs_to :product
	has_many :properties, :dependent => :destroy
	validates :name, :presence => true


	accepts_nested_attributes_for  :properties, reject_if: :all_blank, allow_destroy: true
	
end

product.rb

class Product < ActiveRecord::Base
	has_many :details, :dependent => :destroy
	validates :name, :presence => true


	accepts_nested_attributes_for :details, reject_if: :all_blank, allow_destroy: true
	
end

products_controller.rb

class ProductsController < ApplicationController
	
	# Make an all and new object for every action
	before_filter :load

	# This page has no main page so far
	def index
		@products = Product.all
	end 

	def new
		@product = Product.new
		3.times {@product.details.build}
		@detail = Detail.new
		3.times {@detail.properties.build}
	end

	# Create a new product
	def create
		@product = Product.new(safe_params)
		if @product.save
			respond_to do |format|
				format.html { redirect_to root_path, notice: "Created #{@product.name}."}
				format.js {}
			end
		else
			redirect_to new_product_path
		end
	end


	# Edit a product.. 
	def edit
		@product = Product.find(params[:id])
	end

	# Update a product
	def update 
		@product = Product.find(params[:id])
		if @product.update_attributes(safe_params)
			flash[:notice] = "#{@product.name} updated."
			@products = Product.all
		end
	end

	# Delete product
	def destroy
		@product = Product.find(params[:id])
		@product.destroy
		flash[:notice] = "#{@product.name} deleted."
		@products = Product.all
	end

	# Show products and details
	def show 
		@product = Product.find(params[:id])

		@details = @product.details
		@properties = @details.properties

		# @details = Detail.find_all_by_product_id(params[:id])
		# @detail = Detail.find_by_product_id(params[:id])
	end


	private
	# Load all products
	def load
		@products = Product.all
		@product = Product.new
	end
	# Permit safe params
	def safe_params
		params.require(:product).permit(:product,
														  :name,
														  details_attributes: [:name, :required_at],
														  properties_attributes: [:name]
													  )
	end
end

Property.rb

class Property < ActiveRecord::Base
	belongs_to :detail
end