xdougx/controllers.rb

## controllers.rb
class  ApplicationController < ActionController::Base
  layout 'application'
end

class CategoriesController < ApplicationController
  # app/views/categories/show.html.erb
  def show
    @category = Category.find(params[:id])
  end
end

class SubCategoriesController  < ApplicationController
  # app/views/subcategories/show.html.erb
  def show
    @subcategory = SubCategory.find(params[:id])
  end
end

class ProductController < ApplicationController
  # app/views/products/show.html.erb
  def show
    @product = Product.find(params[:id])
  end
end

## menu_helper.rb
# helpers/menu_helper.rb
module MenuHelper
  def categories_menu
    content_for(:ul) do
      Category.all.map do |category|
        content_for(li) do
          link_to(category.name, category_path(category))
        end
      end
    end.html_safe
  end

  def subcategories_menu
    content_for(:ul) do
      SubCategory.all.map do |subcategory|
        content_for(li) do
          link_to(subcategory.name, category_subcategory_path(subcategory.id, subcategory.category_id))
        end
      end
    end.html_safe
  end

end

## show.html.erb
<section>
  <!-- Monta a Tela -->
</section>

## show_product.html
<section>
  <div>
    <h1><%= @product.name%></h1>
    <h3>SubCategories</h3>
    <!-- montaa tela -->
  </div>
</section>

## template.html
<!DOCTYPE html>
<html>
<head>
  <title>Meu APP</title>
  <%= stylesheet_link_tag    'application', media: 'all' %>
  <%= javascript_include_tag 'application' %>
  <%= csrf_meta_tags %>
</head>
<body>
<nav id="menu_esquerda">
  <%= categories_menu %>
</nav>

<div class="content">
<%= yield %>
<div>

<nav id="menu_direita">
  <%= categories_menu %>
</nav>

</body>
</html>
	class ApplicationController < ActionController::Base
	layout 'application'
	end

	class CategoriesController < ApplicationController
	# app/views/categories/show.html.erb
	def show
	@category = Category.find(params[:id])
	end
	end

	class SubCategoriesController < ApplicationController
	# app/views/subcategories/show.html.erb
	def show
	@subcategory = SubCategory.find(params[:id])
	end
	end

	class ProductController < ApplicationController
	# app/views/products/show.html.erb
	def show
	@product = Product.find(params[:id])
	end
	end
	# helpers/menu_helper.rb
	module MenuHelper
	def categories_menu
	content_for(:ul) do
	Category.all.map do \|category\|
	content_for(li) do
	link_to(category.name, category_path(category))
	end
	end
	end.html_safe
	end

	def subcategories_menu
	content_for(:ul) do
	SubCategory.all.map do \|subcategory\|
	content_for(li) do
	link_to(subcategory.name, category_subcategory_path(subcategory.id, subcategory.category_id))
	end
	end
	end.html_safe
	end

	end
	<section>
	<div>
	<h1><%= @product.name%></h1>
	<h3>SubCategories</h3>
	<!-- montaa tela -->
	</div>
	</section>
	<!DOCTYPE html>
	<html>
	<head>
	<title>Meu APP</title>
	<%= stylesheet_link_tag 'application', media: 'all' %>
	<%= javascript_include_tag 'application' %>
	<%= csrf_meta_tags %>
	</head>
	<body>
	<nav id="menu_esquerda">
	<%= categories_menu %>
	</nav>

	<div class="content">
	<%= yield %>
	<div>

	<nav id="menu_direita">
	<%= categories_menu %>
	</nav>

	</body>
	</html>