Building Extractable Libraries in Rails

Talk given at LVRUG about some conventions for making /lib more agreeable to library extraction.

Transcript

1. Building Extractable Libraries in Rails Thursday, May 3, 12
2. HELLO THERE! I’ m @patricksroberts; I push bits at @iorahealth and herd cats at @bostonrb. Thursday, May 3, 12
3. Some Things I <3 About Rails Thursday, May 3, 12
4. Convention Configuration Thursday, May 3, 12
5. Transport Concerns Business Concerns Thursday, May 3, 12
6. Business Logic Persistence (One can Dream) Thursday, May 3, 12
7. Engines Finally* Fly First Class Thursday, May 3, 12
8. However... I don’ t :( Thursday, May 3, 12
9. We’re still left with many decisions. Thursday, May 3, 12
10. Let’s make some conventions for /lib Thursday, May 3, 12
11. Thursday, May 3, 12
12. Treat /lib as a temple. Thursday, May 3, 12
13. Treat /lib as a temple. Isolate interaction with your domain models. Thursday, May 3, 12
14. /lib is not your junk drawer. Thursday, May 3, 12
15. # 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
16. # 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
17. NO Thursday, May 3, 12
18. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ Thursday, May 3, 12
19. # lib/twitter_wrangler.rb require ‘twitter_wrangler/authentication’ require ‘twitter_wrangler/authorization’ module TwitterWrangler end Thursday, May 3, 12
20. # lib/twitter_wrangler.rb module TwitterWrangler OAUTH_KEY = ‘ABCDEFG1234ZXYZB2324’ end Thursday, May 3, 12
21. NO Thursday, May 3, 12
22. # 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
23. # 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
24. # 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
25. # 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
26. # 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
27. # 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
28. # 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
29. # 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
30. # 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
31. # 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
32. 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
33. Keep your domain models focused on the problem domain. Thursday, May 3, 12
34. Authentication Authorization Queueing Timeouts Caching Prescriptions BMI Appointments Thursday, May 3, 12
35. Common Sense Composition (Also known as the DCI Pattern) Thursday, May 3, 12
36. # 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
37. # 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
38. # 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
39. # 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
40. # 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
41. # 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
42. # 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
43. # 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
44. # 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
45. # 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
46. # 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
47. # 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
48. Web App Library body mass index tweet called Authorization Twitter message Authentication Queueing User sees tweet Thursday, May 3, 12
49. Big Win: Freedom to implement with Google +. (If we were Google employeees) Thursday, May 3, 12
50. Treat /lib with love and respect. Use common sense composition to focus your domain models. Thursday, May 3, 12
51. Thanks! Thursday, May 3, 12