Rails 5 Navigational Menu from deep nested routes - ruby-on-rails

Question

I need to create a dropdown sidebar navigational menu from my Rails 5 nested routes. I have 4 models - locations, categories, subcategories and products. We currently have 4 locations, so I created a query in my application_controller to default the path to our corporate location, San Diego.
From there, I created a category query based on the location query. All is good, I can iterate and print the results to the view, with the category as the title of the dropdown. I need to show the sub-categories in the category dropdown they belong to but I keep getting an undefined error.
I know the nested routes that I have are not ideal for most situations, but this site needs absolute defined urls for search engine ranking...just so you know before you comment on them.
application_controller.rb
class ApplicationController < ActionController::Base
...
before_action :load_vendors
def load_vendors
#location = Location.find_by_name('San Diego')
#category = #location.categories
#subcategory = #category.subcategories
end
...
routes.rb
resources :locations do
resources :categories, path: '' do
resources :subcategories, path: '' do
resources :products, path: ''
end
end
end
_sidebar.html.rb
<div id="ss_menu">
<% #category.each do |c| %>
<div class="ss_button"><%= c.name %></div>
<div class="ss_content">
<ul>
<% #subcategory.each do |s| %>
<li>
<a href="">
<%= s.name %>
</a>
</li>
<% end %>
</ul>
</div>
<% end %>
</div>

Answer 1

First of all, you forgot to add erb extension _sidebar.html.erb.
Moreover, this is what the view should look like:
<div id="ss_menu">
<% #categories.each do |category| %>
<div class="ss_button"><%= category.name %></div>
<div class="ss_content">
<ul>
<% category.subcategories.each do |subcategory| %>
<li>
<%= link_to subcategory.name, ... %>
</li>
<% end %>
</ul>
</div>
<% end %>
</div>
What kind association type do you used for categories?