Source files from a presentation to AtomicJolt about wrapping a general API (Nokogiri) with a domain specific API

000-_init.rb

# rubocop:disable Style/SingleLineMethods
require 'nokogiri'

class Object; alias try send; end
class NilClass; def try(*); nil; end; end

001-data.xml

<tree>
  <person id="p0001">
    <name>
      <full>Frank Edward Redington</full>
      <given>Frank Edward</given>
      <surname>Redington</surname>
    </name>
    <event type="birth">
      <date>1914-04-03</date>
      <location>Elma, Chehalis, Washington, USA</location>
    </event>
    <event type="death">
      <date>1978-12-27</date>
      <location>Medford, Jackson, Oregon, USA</location>
    </event>
  </person>
  <person id="p0002">
    <name>
      <full>Frank Willard Redington</full>
      <given>Frank Willard</given>
      <surname>Redington</surname>
    </name>
    <event type="birth">
      <date>1865-01-22</date>
      <location>Orleans, Ionia, Michigan, USA</location>
    </event>
    <event type="death">
      <date>1930-12-27</date>
      <location>Elma, Grays Harbor, Washington, USA</location>
    </event>
  </person>
  <person id="p0003">
    <name>
      <full>Francis Burrows</full>
      <given>Francis</given>
      <surname>Burrows</surname>
    </name>
    <event type="birth">
      <date>1880-04-10</date>
      <location>Vina, Tehama, California, USA</location>
    </event>
    <event type="death">
      <date>1964-11-27</date>
      <location>Elma, Grays Harbor, Washington, USA</location>
    </event>
  </person>
  <family id="f0001">
    <father id="p0002" />
    <mother id="p0003" />
    <child id="p0001" />
    <event type="marriage">
      <date>1911-12-21</date>
      <location>Oroville, Butte, California, USA</location>
    </event>
    <event type="divorce">
      <date>between 1920 and 1927-12-12</date>
    </event>
  </family>
</tree>

002-raw-api.rb

require './000-_init'

doc = Nokogiri::XML(File.read('001-data.xml'))

frank = doc.at('person#p0001')
puts frank.at('name full').try(:text)
puts frank.at('event[type=death] date').try(:text)

003-functions.rb

require './000-_init'

def find_person(doc, id)
  doc.at("person##{id}")
end

def person_name(record)
  record.at('name full').try(:text)
end

def person_death(record)
  record.at('event[type=death] date').try(:text)
end

doc = Nokogiri::XML(File.read('000-data.xml'))

frank = find_person(doc, 'p0001')
puts person_name(frank)
puts person_death(frank)

004-domain-api.rb

require './000-_init'
require './005-genealogy_take1'
#require './007-genealogy_take2'
#require './009-genealogy_take3'

tree = Genealogy::Tree.from_file('001-data.xml')

frank = tree.find_person('p0001')
puts frank.name.full
puts frank.death.date

005-genealogy_take1.rb

require 'nokogiri'

module Genealogy
  class Tree
    def self.from_file(filename)
      from_xml(File.read(filename))
    end

    def self.from_xml(xml)
      new(Nokogiri::XML(xml))
    end

    def initialize(node)
      @node = node
    end

    def find_person(id)
      person = @node.at("person##{id}")
      person ? Person.new(person) : nil
    end
  end

  # ==================================================================== #

  class Person
    def initialize(node)
      @node = node
    end

    def name
      @name ||= begin
        name = @node.at('name')
        name ? Name.new(name) : nil
      end
    end

    def event(type)
      event = @node.at("event[type=#{type}]")
      event ? Event.new(event) : nil
    end

    def birth
      @birth ||= event :birth
    end

    def death
      @death ||= event :death
    end
  end

  # ==================================================================== #

  class Name
    def initialize(node)
      @node = node
    end

    def full
      @node.at('full').try(:text)
    end

    def surname
      @node.at('surname').try(:text)
    end

    def given
      @node.at('given').try(:text)
    end
  end

  # ==================================================================== #

  class Event
    def initialize(node)
      @node = node
    end

    def date
      @node.at('date').try(:text)
    end

    def location
      @node.at('location').try(:text)
    end
  end
end

006-delegate-example.rb

require 'delegate'

class Wrapper < SimpleDelegator
  def encrypt
    # shhh -- just rot13 here
    tr('a-z', 'n-za-m')
  end
end

string = Wrapper.new('hello world')
puts string.length
puts string.encrypt

007-genealogy_take2.rb

require 'delegate'
require 'nokogiri'

module Genealogy
  class Tree < SimpleDelegator
    def self.from_file(filename)
      from_xml(File.read(filename))
    end

    def self.from_xml(xml)
      new(Nokogiri::XML(xml))
    end

    def find_person(id)
      node = at("person##{id}")
      node ? Person.new(node) : nil
    end
  end

  # ==================================================================== #

  class Person < SimpleDelegator
    def name
      @name ||= begin
        name = at('name')
        name ? Name.new(name) : nil
      end
    end

    def event(type)
      event = at("event[type=#{type}]")
      event ? Event.new(event) : nil
    end

    def birth
      @birth ||= event :birth
    end

    def death
      @death ||= event :death
    end
  end

  # ==================================================================== #

  class Name < SimpleDelegator
    def full
      at('full').try(:text)
    end

    def surname
      at('surname').try(:text)
    end

    def given
      at('given').try(:text)
    end
  end

  # ==================================================================== #

  class Event < SimpleDelegator
    def date
      at('date').try(:text)
    end

    def location
      at('location').try(:text)
    end
  end
end

008-modules.rb

module A
  def hiccup
    'HICCUP!'
  end
end

o = Object.new.extend(A)

puts o.hiccup #-> HICCUP!

009-genealogy_take3.rb

require 'nokogiri'

module Genealogy
  module Tree
    def self.from_file(filename)
      from_xml(File.read(filename))
    end

    def self.from_xml(xml)
      Nokogiri::XML(xml).extend(self)
    end

    def find_person(id)
      person = at("person##{id}")
      person ? person.extend(Person) : nil
    end
  end

  # ==================================================================== #

  module Person
    def name
      @name ||= begin
        name = at('name')
        name ? name.extend(Name) : nil
      end
    end

    def event(type)
      event = at("event[type=#{type}]")
      event ? event.extend(Event) : nil
    end

    def birth
      @birth ||= event :birth
    end

    def death
      @death ||= event :death
    end
  end

  # ==================================================================== #

  module Name
    def full
      at('full').try(:text)
    end

    def given
      at('given').try(:text)
    end

    def surname
      at('surname').try(:text)
    end
  end

  # ==================================================================== #

  module Event
    def date
      at('date').try(:text)
    end

    def location
      at('location').try(:text)
    end
  end
end