classes.rb

class MyFile
  attr_accessor :name, :size, :content, :extension

  def initialize(args)
    @name = args[:name]
    @size = args[:size]
    @content = args[:content]
    @extension = args[:extension]
  end

  def edit(content)
    @content = content
  end
end

class Storage
  attr_accessor :brand, :speed, :capacity, :files

  def initialize(args)
    @brand = args[:brand]
    @speed = args[:speed]
    @capacity = args[:capacity]
    @files = args[:files] || []
  end

  def add_file(file)
    @files << file
  end

  def used_space
    @files.reduce(0) do |total_size, file|
      total_size += file.size
    end
  end
end

class ImageFile < MyFile
end

class TextFile < MyFile
end