.rb

require 'n_cipher/argument_validation'

class Configuration
  include NCipher::ArgumentValidation

  def initialize(hash)
    hash.each_pair(&method(:define_accessor))
    define_singleton_method(:reset) { initialize(hash); self }
  end

  def to_h
    self.instance_variables.map(&:to_s).each_with_object({}) do |key, rtn_hash|
      rtn_hash[key.sub(/\A@/, '').to_sym] = self.instance_variable_get(key)
    end
  end

  def add_validation(method_name, message=nil, &validation)
    self.singleton_class.class_eval { args_validation(method_name, message, &validation) }
  end

  args_validation :initialize, 'Argument should be a hash object.' do |object|
    object.is_a?(Hash)
  end

  args_validation :add_validation, 'undefined method' do |name|
    self.singleton_class.method_defined?(name)
  end

  private

  def define_accessor(name, value)
    instance_variable_set("@#{name}", value)
    define_singleton_method(name) { self.instance_variable_get("@#{name}") }
    define_singleton_method("#{name}=") {|arg| self.instance_variable_set("@#{name}", arg) }
  end
end

config = Configuration.new(:foo => :bar)