Ruby on Rails: render - display menu, cart on every page of the site?

Question

Ruby on Rails

Good evening! Interested in the following question, how to add a shopping cart for an online store to each page of the site (basket as in the Agile Web Dev book), I have 4 models - Category, Product, Cart, Post.
layout application.html.erb

<%= render :partial => 'categories/cart', :locals => {:cart => @cart}%>

partial_cart.html.erb _

&lt;% if @cart.blank? %&gt;<br/>
&lt;% else %&gt;<br/>
 &lt;% for item in @cart.items %&gt;<br/>
 &lt;%= item.quantity %&gt; × &lt;%=h item.title %&gt;&lt;%= number_to_currency(item.price) %&gt;<br/>
 &lt;% end %&gt;<br/>
Итого: &lt;%= number_to_currency(@cart.total_price) %&gt;<br/>
 &lt;%= button_to 'Очистить корзину', :controller =&gt; 'categories', :action =&gt; 'empty_cart'%&gt;<br/>
&lt;% end %&gt;

In this scenario, the cart is displayed only in the view of the Categories controller. I can’t figure out how to get the necessary data from the session[:cart] session or in some other way.
And another question, how to properly display the menu on each page, now something like this:

<%= render :partial => 'posts/post', :collections => Post.all %>

Thanks for answers.

Answer 1

If you cannot get the cart from the session, then take a closer look in the book where you took the cart from, find_cart method:

def find_cart
    session[:cart] ||= Cart.new
end

If the problem is simply that the cart object is assigned to the @cart variable in all templates, then move the find_cart method to the application_controller.rb file and include this method in before_filter in the same file. Then your cart will be unloaded from the session into the @cart variable in all controllers.
ps Do not copy the HTML code directly, the parser ate half of the code.