gistfile1.rb

# /app/controllers/store_controller.rb
class StoreController < ApplicationController
  def index
  	@products = Product.all
    
    session[:counter] ||= 0
    @count = session[:counter] += 1
  end
end

# /app/views/store/index.html.erb
...
<h2>The count <%= count %></h2>
...