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Building Extractable Libraries in Rails Thursday, May 3, 12

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HELLO THERE! I’ m @patricksroberts; I push bits at @iorahealth and herd cats at @bostonrb. Thursday, May 3, 12

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Some Things I <3 About Rails Thursday, May 3, 12

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Convention Configuration Thursday, May 3, 12

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Transport Concerns Business Concerns Thursday, May 3, 12

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Business Logic Persistence (One can Dream) Thursday, May 3, 12

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Engines Finally* Fly First Class Thursday, May 3, 12

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However... I don’ t :( Thursday, May 3, 12

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We’re still left with many decisions. Thursday, May 3, 12

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Let’s make some conventions for /lib Thursday, May 3, 12

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Thursday, May 3, 12

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Treat /lib as a temple. Thursday, May 3, 12

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Treat /lib as a temple. Isolate interaction with your domain models. Thursday, May 3, 12

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/lib is not your junk drawer. Thursday, May 3, 12

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# config/application.rb # Custom directories with classes and modules you want to be autoloadable. config.autoload_paths += %W(#{config.root}/lib) Thursday, May 3, 12

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# config/application.rb # Custom directories with classes and modules you want to be autoloadable. config.autoload_paths += %W(#{config.root}/lib) Thursday, May 3, 12

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NO Thursday, May 3, 12

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# config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ Thursday, May 3, 12

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# lib/twitter_wrangler.rb require ‘twitter_wrangler/authentication’ require ‘twitter_wrangler/authorization’ module TwitterWrangler end Thursday, May 3, 12

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# lib/twitter_wrangler.rb module TwitterWrangler OAUTH_KEY = ‘ABCDEFG1234ZXYZB2324’ end Thursday, May 3, 12

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NO Thursday, May 3, 12

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# config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end Thursday, May 3, 12

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# config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end Thursday, May 3, 12

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# config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end Thursday, May 3, 12

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# config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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# lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end Thursday, May 3, 12

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Chaos is hard to undo on a large library; starting with order is easy. At any moment that code in /lib might need to be a gem. Thursday, May 3, 12

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Keep your domain models focused on the problem domain. Thursday, May 3, 12

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Authentication Authorization Queueing Timeouts Caching Prescriptions BMI Appointments Thursday, May 3, 12

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Common Sense Composition (Also known as the DCI Pattern) Thursday, May 3, 12

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# lib/twitter_wrangler/roles/tweeting_patient.rb module TwitterWrangler::Roles::TweetingPatient def bmi_twitter_message “Today my BMI is #{body_mass_index} and I’m #{percent_of_body_mass_index_goal} from my goal of #{body_mass_index_goal}!” end end Thursday, May 3, 12

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# lib/twitter_wrangler/roles/tweeting_patient.rb module TwitterWrangler::Roles::TweetingPatient def bmi_twitter_message “Today my BMI is #{body_mass_index} and I’m #{percent_of_body_mass_index_goal} from my goal of #{body_mass_index_goal}!” end end Thursday, May 3, 12

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# lib/twitter_wrangler/roles/tweeting_patient.rb module TwitterWrangler::Roles::TweetingPatient def bmi_twitter_message “Today my BMI is #{body_mass_index} and I’m #{percent_of_body_mass_index_goal} from my goal of #{body_mass_index_goal}!” end end Thursday, May 3, 12

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# lib/twitter_wrangler/support/fake_patient.rb class FakePatient def body_mass_index;27;end def percent_of_body_mass_index_goal;”95%”;end def body_mass_index_goal;25;end end # spec/twitter_wrangler/roles/tweeting_patient_spec.rb describe TweetingPatient do let(:patient) { FakePatient.new } before { FakePatient.extend TweetingPatient } it ‘asserts some fantastic things’ do #GLORIOUS SPECS end end Thursday, May 3, 12

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# spec/twitter_wrangler/roles/tweeting_patient_spec.rb describe TweetingPatient do let(:patient) { mock() } before do patient.stubs({body_mass_index: 27, percent_of_body_mass_index_goal: “95%” body_mass_index_goal: 25 }) patient.extend TweetingPatient end it ‘asserts some fantastic things’ do #GLORIOUS SPECS end end Thursday, May 3, 12

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# lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_accessor: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end Thursday, May 3, 12

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# lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_accessor: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end Thursday, May 3, 12

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# lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_accessor: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end Thursday, May 3, 12

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# lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_accessor: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end Thursday, May 3, 12

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# lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_accessor: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end Thursday, May 3, 12

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# spec/models/patient_bmi_observer_spec.rb describe PatientBMIObserver do let(:bmi_update) { mock() } before do BMITwitterUpdate.stubs(:new).returns bmi_update bmi_update.stubs :call end it ‘sends a twitter update on mah BMI’ do # expect #call to have been called once end end Thursday, May 3, 12

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# spec/models/patient_bmi_observer_spec.rb describe PatientBMIObserver do let(:bmi_update) { mock() } before do BMITwitterUpdate.stubs(:new).returns bmi_update bmi_update.stubs :call end it ‘sends a twitter update on mah BMI’ do # expect #call to have been called once end end Thursday, May 3, 12

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Web App Library body mass index tweet called Authorization Twitter message Authentication Queueing User sees tweet Thursday, May 3, 12

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Big Win: Freedom to implement with Google +. (If we were Google employeees) Thursday, May 3, 12

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Treat /lib with love and respect. Use common sense composition to focus your domain models. Thursday, May 3, 12

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Thanks! Thursday, May 3, 12