Adventures In The Hexagonal (ShRUG November 12)

I’m passionate about TDD. I hate slow tests. I write app’s that work with Rails. I used to think these three things, (tests,speed,rails) was a classic ‘pick any two problem’, now I don’t.

Let’s talk about building Rails apps; how we can use hexagonal techniques to create code that is loosley coupled, isolated, and hopefully better designed; how we can use the existing Rails ecosystem to achieve this, and hopefully present a few ideas on where we can take this.

Given at the november 2012 meetup of the Sheffield Ruby User Group

Transcript

1. ADVENTURES IN THE HEXAGONAL JON ROWE Tuesday, 13 November 12
2. HEXAWAT? Tuesday, 13 November 12
3. HEXAWAT? Who is this crazy person? Tuesday, 13 November 12
4. HEXAWAT? Who is this crazy person? What is he talking about? Tuesday, 13 November 12
5. HEXAWAT? Who is this crazy person? What is he talking about? Why is the rum gone? Tuesday, 13 November 12
6. HEXAGONAL Tuesday, 13 November 12
7. HEXAGONAL Hexagonal Architecture Tuesday, 13 November 12
8. HEXAGONAL Hexagonal Architecture Describes the structure of an app Tuesday, 13 November 12
9. HISTORY Originally by Alistair Cockburn Tuesday, 13 November 12
10. HISTORY Originally by Alistair Cockburn Also called “Ports and Adaptors” Tuesday, 13 November 12
11. HISTORY Back in t’day Tuesday, 13 November 12
12. HISTORY Back in t’day 3 Layer Architecture Tuesday, 13 November 12
13. HISTORY Back in t’day 3 Layer Architecture GUI => Logic => DB Tuesday, 13 November 12
14. Application Tuesday, 13 November 12
15. HEXAGONAL Tuesday, 13 November 12
16. HEXAGONAL Decouple the application Tuesday, 13 November 12
17. HEXAGONAL Decouple the application Make the business logic the focus Tuesday, 13 November 12
18. HEXAGONAL Decouple the application Make the business logic the focus Provide adaptors for technology Tuesday, 13 November 12
19. HEXAGONAL Decouple the application Make the business logic the focus Provide adaptors for technology Provide adaptors for I/O Tuesday, 13 November 12
20. HEXAGONAL RAILS Tuesday, 13 November 12
21. HEXAGONAL RAILS Describes structure of application Tuesday, 13 November 12
22. HEXAGONAL RAILS Describes structure of application but... Rails is not the application Tuesday, 13 November 12
23. HEXAGONAL RAILS Describes structure of application but... Rails is not the application ... Rails is the HTTP Adaptor Tuesday, 13 November 12
24. HEXAGONAL RAILS Describes building apps *with* Rails Tuesday, 13 November 12
25. Application Tuesday, 13 November 12
26. RAILS CMD LINE LOGGING DB Application Tuesday, 13 November 12
27. WHY? Tuesday, 13 November 12
28. WHY? Separate responsibilities Tuesday, 13 November 12
29. WHY? Separate responsibilities Not just SOC Tuesday, 13 November 12
30. WHY? Separate responsibilities Not just SOC Separate business logic from web logic Tuesday, 13 November 12
31. WHY? Tuesday, 13 November 12
32. WHY? Push dependencies inwards Tuesday, 13 November 12
33. WHY? Push dependencies inwards Make things more explicit Tuesday, 13 November 12
34. WHY? Push dependencies inwards Make things more explicit Easier to see coupling / dependancies Tuesday, 13 November 12
35. WHY? Tuesday, 13 November 12
36. WHY? Modular code Tuesday, 13 November 12
37. WHY? Modular code Isolated / Testable code Tuesday, 13 November 12
38. WHY? Modular code Isolated / Testable code Cleaner code Tuesday, 13 November 12
39. INTERLUDE Tuesday, 13 November 12
40. HOW? Tuesday, 13 November 12
41. HOW? Dependency Injection / Inversion Tuesday, 13 November 12
42. HOW? Dependency Injection / Inversion Pure Ruby service classes Tuesday, 13 November 12
43. HOW? Dependency Injection / Inversion Pure Ruby service classes Define an API / Duck Typing Tuesday, 13 November 12
44. CONTROLLERS Tuesday, 13 November 12
45. CONTROLLERS Controller provides what is needed Tuesday, 13 November 12
46. CONTROLLERS Controller provides what is needed Controller provides how to respond Tuesday, 13 November 12
47. class AccountController < ApplicationController def update ServiceClass.perform(self,params[:things]) end def success(model) redirect_to model end def failure(model) render "edit", locals: { form: model } end end Tuesday, 13 November 12
48. class HexagonalController < ApplicationController def update ServiceClass.perform( FormResponse.new(self), params[:things] ) end end class FormResponse < SimpleDelegator def success(model) redirect_to model end def failure(model) render "edit", locals: { form: model } end end Tuesday, 13 November 12
49. RESPONDERS Tuesday, 13 November 12
50. RESPONDERS Wrap response logic Tuesday, 13 November 12
51. RESPONDERS Wrap response logic Can be reused Tuesday, 13 November 12
52. RESPONDERS Wrap response logic Can be reused Can be stacked Tuesday, 13 November 12
53. ServiceClass.perform( AuthorizationResponse.new(FormResponse.new(self)), params[:things] ) class FormResponse < SimpleDelegator def success(model) redirect_to model end def failure(model) render "edit", locals: { form: model } end end class AuthorizationResponse < SimpleDelegator def access_denied redirect_to "login" end end Tuesday, 13 November 12
54. CORE Tuesday, 13 November 12
55. CORE Do things without knowledge of Rails Tuesday, 13 November 12
56. CORE Do things without knowledge of Rails Respond back with results Tuesday, 13 November 12
57. class AnotherServiceClass def initialize(responder, model, store) @responder, @model, @store = responder, model, store end def perform(attrs) model.new_thing = attrs.fetch :new_thing, 'Default' if store.save model @responder.success model else @responder.failure model end end end Tuesday, 13 November 12
58. DEPENDENCY INJECTION Tuesday, 13 November 12
59. DEPENDENCY INJECTION Not scary Tuesday, 13 November 12
60. DEPENDENCY INJECTION Not scary Can be simple plain Ruby Tuesday, 13 November 12
61. DEPENDENCY INJECTION Not scary Can be simple plain Ruby Pass in what you need Tuesday, 13 November 12
62. SIDE NOTE Tuesday, 13 November 12
63. SIDE NOTE Use Rack, Use Routes Tuesday, 13 November 12
64. SIDE NOTE Use Rack, Use Routes Provide info before the controller Tuesday, 13 November 12
65. SIDE NOTE Use Rack, Use Routes Provide info before the controller E.g. Warden / Rack env for users. Tuesday, 13 November 12
66. PERSISTENCE Tuesday, 13 November 12
67. PERSISTENCE Not very talked about Tuesday, 13 November 12
68. PERSISTENCE Not very talked about No consensus Tuesday, 13 November 12
69. PERSISTENCE Not very talked about No consensus Still hard, how do we deal with AR? Tuesday, 13 November 12
70. PERSISTENCE Tuesday, 13 November 12
71. PERSISTENCE Wrap ORM API Tuesday, 13 November 12
72. PERSISTENCE Wrap ORM API Create repositories that pass back objects Tuesday, 13 November 12
73. PERSISTENCE Wrap ORM API Create repositories that pass back objects Use DataMapper pattern? Tuesday, 13 November 12
74. TOOLS Tuesday, 13 November 12
75. TOOLS What can we use to streamline this? Tuesday, 13 November 12
76. OBJECTIFY Tuesday, 13 November 12
77. OBJECTIFY Not strictly Hexagonal Tuesday, 13 November 12
78. OBJECTIFY Not strictly Hexagonal Request Execution Framework Tuesday, 13 November 12
79. OBJECTIFY Not strictly Hexagonal Request Execution Framework Dependency Injection aka Raptor Tuesday, 13 November 12
80. class RequiresLoginPolicy def allowed?(current_user) !current_user.nil? end end class UnauthenticatedResponder def call(format, routes) format.any { redirect_to routes.login_url } end end MyApp::Application.routes.draw do objectify.defaults :policies => :requires_login objectify.policy_responders({ :requires_login => :unauthenticated }) objectify.resources :pictures end Tuesday, 13 November 12
81. class PicturesCreateService def call(current_user, params) current_user.pictures.create params[:picture] end end class PicturesCreateResponder def call(service_result, format) if service_result.persisted? format.any { redirect_to service_result } else format.any { render template: "new.html.erb" } end end end Tuesday, 13 November 12
82. MORPHINE Tuesday, 13 November 12
83. MORPHINE Lightweight DI tool Tuesday, 13 November 12
84. class Application include Morphine register :service do Service.new client end def perform_action(client) service.authorize! end end Tuesday, 13 November 12
85. describe ‘test’ do let(:client) { double ‘client’ } let(:service) { double ‘service’ } let(:application) { Application.new } before { application.service = service } subject { application.perform_action client } specify “behaviour” end class Controller def action Application.new.perform_action current_user end end Tuesday, 13 November 12
86. PERPETUITY Tuesday, 13 November 12
87. PERPETUITY DataMapper implementation Tuesday, 13 November 12
88. PERPETUITY DataMapper implementation Define mappers for PORO Objects Tuesday, 13 November 12
89. PERPETUITY DataMapper implementation Define mappers for PORO Objects Would probably still need a wrapper Tuesday, 13 November 12
90. class Article attr_accessor :title, :body end Perpetuity.generate_mapper_for Article do attribute :title, String attribute :body, String end article = Article.new article.title = 'New Article' article.body = 'This is an article.' Perpetuity[Article].insert article Tuesday, 13 November 12
91. class Library def initialize(responder, store) @responder, @store = responder, store end attr_reader :responder, store def create(type,attrs) obj = type.new obj.title = attrs[:title] obj.body = attrs[:body] store.insert article responder.success end end store = Perpetuity[Article] lib = ArticleLibrary.new response, store, lib.create Article, params[:article] Tuesday, 13 November 12
92. SUMMARY Tuesday, 13 November 12
93. SUMMARY Push / Inject dependencies Tuesday, 13 November 12
94. SUMMARY Push / Inject dependencies Give application logic ways to respond Tuesday, 13 November 12
95. SUMMARY Push / Inject dependencies Give application logic ways to respond Isolate components Tuesday, 13 November 12
96. SUMMARY Push / Inject dependencies Give application logic ways to respond Isolate components Define *your* API Tuesday, 13 November 12
97. BENEFITS Tuesday, 13 November 12
98. BENEFITS Cleaner code Tuesday, 13 November 12
99. BENEFITS Cleaner code Faster tests Tuesday, 13 November 12
100. BENEFITS Cleaner code Faster tests Easier to adapt Tuesday, 13 November 12
101. THANKS Jon Rowe @jonrowe (Twitter, GitHub, etc) http://jonrowe.co.uk Tuesday, 13 November 12
102. LINKS Tuesday, 13 November 12
103. LINKS https://github.com/bitlove/objectify Tuesday, 13 November 12
104. LINKS https://github.com/bitlove/objectify https://github.com/bkeepers/morphine Tuesday, 13 November 12
105. LINKS https://github.com/bitlove/objectify https://github.com/bkeepers/morphine https://github.com/jgaskins/perpetuity Tuesday, 13 November 12
106. LINKS https://github.com/bitlove/objectify https://github.com/bkeepers/morphine https://github.com/jgaskins/perpetuity Tuesday, 13 November 12
107. LINKS Tuesday, 13 November 12
108. LINKS http://weblog.therealadam.com/ 2011/10/09/your-frienemy-the-orm/ Tuesday, 13 November 12
109. LINKS http://weblog.therealadam.com/ 2011/10/09/your-frienemy-the-orm/ http://rubyrogues.com/078-rr- hexagonal-rails-with-matt-wynne-and- kevin-rutherford/ Tuesday, 13 November 12