whiteboard.rb

class Whiteboard
  attr_accessor :contents

  def initialize(contents = [])
    @contents = contents
  end

  def erase
    @contents= []
  end
end

class DryEraseMarker
  attr_reader :color, :capacity
    def initialize(color)
      @color = color
      @capacity = 100
    end

    INK_USE_PER_CHARACTER = 0.01
    def write(contents, whiteboard)
      @capacity = @capacity - (INK_USE_PER_CHARACTER * contents.length)
      whiteboard.contents << contents
    end

    def empty?
      if @capacity==0
        false
      else
        true
      end
    end
end


whiteboard = Whiteboard.new
black_marker = DryEraseMarker.new('black')

black_marker.write('Hello Launchers', whiteboard)
black_marker.write('My name is Slim Shady', whiteboard)


puts whiteboard.contents

puts whiteboard.contents.length

puts whiteboard.erase

puts whiteboard.contents.length