feed.rb

module Model
  def initialize(attributes)
    self.attributes = attributes
  end

  def attributes=(hash)
    hash.each do |k, v|
      send :"#{k}=", v
    end
  end
end

def sanitize_html(s)
  s.strip #todo
end

class Feed
  include Model

  attr_accessor :title

  attr_reader :description, :published_at

  def description=(value)
    @description = sanitize_html(value)
  end

  def published_at=(value)
    case value
    when Time
      @published_at = value
    when String
      @published_at = Time.new(value)
    when nil
      @published_at = nil
    else
      raise 'bad value'
    end
  end
end

Feed.new(title: 'hey', description: ' a great story ', published_at: Time.now)