gistfile1.rb

require 'rubygems'
require 'json'

module Base
  def fields
    @fields ||= params.is_a?(String) ? JSON.parse(params) : params
  end

  def [](field)
    fields[field]
  end

  def []=(field, value)
    @fields[field] = value
  end  

  def keys
    fields.keys
  end

  def to_json
    fields.to_json
  end

  def method_missing(meth, *args, &block)
    method_name = meth.to_s
    if keys.include?(method_name)
      self[method_name]
    elsif keys.include?(method_name.gsub!('=', ''))
      self[method_name] = args.first
    else
      super
    end
  end
end

Room = Struct.new :params do
  include Base
end

Hotel = Struct.new :params do
  include Base
  def rooms
    @rooms ||= self["rooms"].collect{|room| Room.new(room)}
  end
end

hotel = Hotel.new("{\"name\":\"Nadiya\",\"location\":\"Ivano-Frankivsk\",\"rooms\":[{\"name\":\"Lux\"},{\"name\":\"Standard\"}]}")

puts hotel.name
puts hotel.rooms.first.name

hotel.name = "NEW NAME"
puts hotel.name

puts hotel.to_json