An example to demonstrate Proxy Pattern implemented in Ruby https://repl.it/C6R2/3

proxy_pattern.rb

class CarRental
  def initialize(cars)
    @cars = cars
  end
  def rent_out(n)
    @cars -= n
  end
  def buy(n)
    @cars += n
  end
  def inventory
    puts "Cars left: #{@cars}"
  end
  # An overwritten Object Class method
  def to_s
    puts "Inspecting cars: #{@cars.inspect}"
  end
end

class RentalProxy < BasicObject
  def initialize(cars)
    @history = []
    @rental = ::CarRental.new(cars)
    @history << [:init, cars]
  end
  def method_missing(method, *args, &block)
    @history << [method, args]
    @rental.send(method, *args, &block)
  end
  def history
    @history
  end
end

car_rental = RentalProxy.new(20)
puts car_rental.history.to_s

car_rental.inventory
car_rental.rent_out(2)
car_rental.inventory

car_rental.buy(4)
car_rental.inventory

puts car_rental.history.to_s

car_rental.to_s

Console Output

ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
>>> [[:init, 20]]
Cars left: 20
Cars left: 18
Cars left: 22
[[:init, 20], [:inventory, []], [:rent_out, [2]], [:inventory, []], [:buy, [4]], [:inventory, []]]
Inspecting cars: 22