example.rb

module Tracking
	def create(customername)
		customers << new(customername)
	end

	def customers
		@customers ||= []
	end
end


class Customer
	extend Tracking

	attr_accessor :name

	def initialize(name)
		@name = name
	end

	def to_s
		"[#{@name}]"
	end

end


Customer.create("Peter")
Customer.create("Angie")
Customer.create("Bill")
puts Customer.customers.inspect