基于多线程的全局变量

def current_nation

    default_nation = (current_contact && current_contact&.company&.country) ? current_contact&.company&.country : "United States"

    cookie_country_id = cookies['country_id'].to_i

    contact_country_id = current_contact.try(:ship_nation).to_i

    country_id = cookie_country_id > 0 ? cookie_country_id : contact_country_id

    @current_nation = Nation.where(id: country_id).first

    if @current_nation.blank?

      cookies.delete('country_id')

      @current_nation = Nation.where(name: default_nation ).first

    end

    Product.current_nation = @current_nation&.name

    @current_nation

  end


class Product < ApplicationRecord 
  thread_mattr_accessor :current_nation, instance_accessor: true
end