Inefficient but expressive

hash.csspath.rb

Hash.class_eval do
  # returns an array of values
  def csspath(path, options = {})
    Nokogiri::HTML(self.to_xml).css(path.dasherize).collect {|element|
      result = Hash.from_xml(element.to_s)
      (options[:include_keys] ? result : result.values.first)
    }
  end
end

sample.rb

hash = {
  cart: {
    created_at: "2014-05-16 04:51:13 UTC",
    id: "cart:1234",
    line_items: [
      {
        title: "Item A",
        price: "123.45"
      },
      {
        title: "Item B",
        price: "234.56"
      }
    ]
  },
  customer: {
    name: "John",
    email: "john.appleseed@example.com"
  }
}

hash.csspath('cart created_at, nothing here, line_items title, customer name')
# => ["2014-05-16 04:51:13 UTC", "Item A", "Item B", "John"] 

hash.csspath('cart created_at, nothing here, line_items title, customer name', include_keys: true)
# => [{"created_at"=>"2014-05-16 04:51:13 UTC"}, {"title"=>"Item A"}, {"title"=>"Item B"}, {"name"=>"John"}]