我最终创建了一个基于构建器和策略模式的解决方案。我使用生成器模式将解析和构建逻辑提取到自己的类中。这使我能够轻松地分别添加新的解析器和构建器。我使用策略模式来实现单独的解析和构建逻辑,因为该逻辑取决于我的输入和输出格式。
下图显示了我的解决方案的 UML 图。
下面的清单显示了我的 Ruby 实现。实现有点微不足道,因为我正在构建的对象相当简单。对于那些认为这段代码臃肿且类似 Java 的人来说,我认为这实际上是一个很好的设计。我承认,在这种微不足道的情况下,我可以直接将构造方法直接构建到我的业务对象中。但是,我没有在其他应用程序中构建水果,而是构建相当复杂的对象,因此将解析、构建和业务逻辑分开似乎是一个好主意。
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'))