value_object.rb

module ValueObject
  def ==(other)
    case other
    when ValueObject
      self.object_value == other.object_value
    else
      false
    end
  end

  def eql?(other)
    ( self.class == other.class ) && ( self == other )
  end

  def hash
    object_value.hash
  end

  def to_hash
    object_presentation.deep_stringify_keys
  end

  def object_presentation
    to_json_object(presentation_properties)
  end

  def presentation_properties
    value_properties
  end

  def object_value
    to_json_object(value_properties)
  end

  def value_properties
    self.instance_values.keys.sort
  end

  private

  def to_json_object(property_names)
    property_names.map(&:to_sym).map do |property_name|
      [ property_name, self.send(property_name) ]
    end.to_h
  end
end