for medium article 'Rails fast collection render'

prerender.rb

class Product <ActiveRecord::Base
 after_commit :prerender
 def prerender
  keys = [ [:user, :admin, :moderator, nil], [:ru, :en ] ]
  keys.pop.product(*keys).each do |lr|
   # lr - locale + role
   ApplicationController.render(
    assigns: {locals: {product: self, role: lr[1], locale: lr[0]} },
    inline: '<% render partial: "products/product", locals: @locals %>')
    #of course products/_product.html.slim must start with
    #-cache[product, ...] do
  end #each
 end #prerender
end #Product