tv.rb

class Television
  attr_accessor :manufacturer, :hd_compliant, :aspect_ratio, :screen_size

  def initialize(manufacturer, hd_compliant, aspect_ratio, screen_size)
    @manufacturer = manufacturer
    @hd_compliant = hd_compliant
    @aspect_ratio = aspect_ratio
    @screen_size = screen_size
  end

  def change_channel(channel)
    @channel = channel
  end

  def to_s
    result = "This is a #{@manufacturer} TV"
    result += " with an aspect ratio of #{@aspect_ratio}"
    result += ", a screen size of #{@screen_size} inches"
    result += ", and is tuned to #{@channel.name}" if !@channel.nil?
    return result
  end
end

class Channel
  attr_accessor :name, :channel_number

  def initialize(name, channel_number)
    @name = name
    @channel_number = channel_number
  end
end

class Show
  attr_accessor :name, :channel, :host, :time

  def initialize(name, channel, host, time)
    @name = name
    @channel = channel
    @host = host
    @time = time
  end
end

tv = Television.new("Sony", true, "16:9", 42)
comedy_central = Channel.new("Comedy Central", 57)
the_daily_show = Show.new("The Daily Show", comedy_central, "Jon Stewart", "6pm")

puts tv
tv.change_channel(comedy_central)
puts tv