ActiveRecord like model with validations and dynamic attributes

model.rb

require 'rubygems'
require 'active_model'
require 'active_support'

class Model
  include ActiveModel::Validations
  include ActiveModel::Conversion
  extend ActiveModel::Naming
  
  def initialize(attributes = {})
    attributes.each { |name, value|
      create_attr(name, value)
    }
  end
  
  def persisted?
    false
  end
  
  def create_attr(name, value)
    self.class.class_eval { attr_accessor name.to_sym } 
    
    if(value.instance_of?(Array))
      send "#{name}=", value.collect { |v| class_for(name).new(v) }
    else
      send "#{name}=", value
    end
  end
  
  private
    def method_missing(method_name, *args, &block)
      match = method_name.to_s.match(/(.*?)([?]?)$/)      
      case match[2]
      when "?"
        instance_variable_defined?("@#{match[1]}")  
      end
    end
    
    def class_for(key)
      Object.const_get(key.to_s.classify)
    end
end