For [Design Pattern: Strategy and Burger](https://medium.com/@sihui/design-pattern-strategy-and-burger-d31541d295a9)

strategy_burger.rb

# Concrete Strategy
class GrilledChickenStuffing
  def cook
    stuffing = []
    stuffing << 'sliced tomato'
    stuffing << 'lettuce'
    stuffing << 'grilled chicken breast'
    stuffing
  end
end

class BeefPattyStuffing
  def cook
    stuffing = []
    stuffing << 'cheese'
    stuffing << 'grilled beef patty'
    stuffing
  end
end

# Context
class Burger
  attr_reader :top_bun, :bottom_bun
  attr_accessor :stuffing

  def initialize(stuffing)
    @top_bun = TOP_BUN
    @stuffing = stuffing
    @bottom_bun = BOTTOM_BUN
  end

  def cook
    burger = []
    burger << top_bun.cook
    burger << stuffing.cook
    burger << bottom_bun.cook
    burger
  end
end

chicken_burger = Burger.new(GrilledChickenStuffing.new)
cheese_burger = Burger.new(BeefPattyStuffing.new)

# change the chicken_burger to a cheese burger
chicken_burger.stuffing = BeefPattyStuffing.new