Module#prepend replacing :alias_method

prepend_method.rb

class Earphone
  def left
    puts "Playing on left."
    play(0)
  end

  def right
    puts "Playing on right."
    play(1)
  end

  # this.
  def left_with_bit_rate
    puts "Left with bit rate."
    left_without_bit_rate
    right_without_bit_rate
  end
  alias_method :left_without_bit_rate, :left
  alias_method :left, :left_with_bit_rate

  def right_with_bit_rate
    puts "Right with bit rate."
    right_without_bit_rate
  end
  alias_method :right_without_bit_rate, :right
  alias_method :right, :right_with_bit_rate

  private
  def play(direction)
    puts direction == 0 ? "Left" : "Right"
  end
end

phone = Earphone.new

phone.left
phone.right