问是否有以不同格式序列化和反序列化对象层次结构的模式？

EN

require 'nokogiri'
require 'json'

class Fruit

  attr_accessor :name
  attr_accessor :size
  attr_accessor :color

  def initialize(attrs = {})
    self.name = attrs[:name]
    self.size = attrs[:size]
    self.color = attrs[:color]
  end

  def to_s
    "#{size} #{color} #{name}"
  end

end

class FruitBuilder

  def self.build(opts = {}, &block)
    builder = new(opts)
    builder.instance_eval(&block)
    builder.result
  end

  def self.delegate(method, target)
    method = method.to_sym
    target = target.to_sym

    define_method(method) do |*attrs, &block|
      send(target).send(method, *attrs, &block)
    end
  end

end

class FruitObjectBuilder < FruitBuilder

  attr_reader :fruit

  delegate :name=,  :fruit
  delegate :size=,  :fruit
  delegate :color=, :fruit

  def initialize(opts = {})
    @fruit = Fruit.new
  end

  def result
    @fruit
  end

end

class FruitXMLBuilder < FruitBuilder

  attr_reader :document

  def initialize(opts = {})
    @document = Nokogiri::XML::Document.new
  end

  def name=(name)
    add_text_node(root, 'name', name)
  end

  def size=(size)
    add_text_node(root, 'size', size)
  end

  def color=(color)
    add_text_node(root, 'color', color)
  end

  def result
    document.to_s
  end

  private

  def add_text_node(parent, name, content)
    text = Nokogiri::XML::Text.new(content, document)
    element = Nokogiri::XML::Element.new(name, document)

    element.add_child(text)
    parent.add_child(element)
  end

  def root
    document.root ||= create_root
  end

  def create_root
    document.add_child(Nokogiri::XML::Element.new('fruit', document))
  end

end

class FruitJSONBuilder < FruitBuilder

  attr_reader :fruit

  def initialize(opts = {})
    @fruit = Struct.new(:name, :size, :color).new
  end

  delegate :name=,  :fruit
  delegate :size=,  :fruit
  delegate :color=, :fruit

  def result
    Hash[*fruit.members.zip(fruit.values).flatten].to_json
  end

end

class FruitParser

  attr_reader :builder

  def initialize(builder)
    @builder = builder
  end

  def build(*attrs, &block)
    builder.build(*attrs, &block)
  end

end

class FruitObjectParser < FruitParser

  def parse(other_fruit)
    build do |fruit|
      fruit.name  = other_fruit.name
      fruit.size  = other_fruit.size
      fruit.color = other_fruit.color
    end
  end

end

class FruitXMLParser < FruitParser

  def parse(xml)
    document = Nokogiri::XML(xml)

    build do |fruit|
      fruit.name  = document.xpath('/fruit/name').first.text.strip
      fruit.size  = document.xpath('/fruit/size').first.text.strip
      fruit.color = document.xpath('/fruit/color').first.text.strip
    end
  end

end

class FruitJSONParser < FruitParser

  def parse(json)
    attrs = JSON.parse(json)

    build do |fruit|
      fruit.name  = attrs['name']
      fruit.size  = attrs['size']
      fruit.color = attrs['color']
    end
  end

end

# -- Main program ----------------------------------------------------------

p = FruitJSONParser.new(FruitXMLBuilder)
puts p.parse('{"name":"Apple","size":"Big","color":"Red"}')

p = FruitXMLParser.new(FruitObjectBuilder)
puts p.parse('<fruit><name>Apple</name><size>Big</size><color>Red</color></fruit>')

p = FruitObjectParser.new(FruitJSONBuilder)
puts p.parse(Fruit.new(:name => 'Apple', :color => 'Red', :size => 'Big'))