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
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2. HEXAWAT?
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3. HEXAWAT?
   Who is this crazy person?
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4. HEXAWAT?
   Who is this crazy person?
   What is he talking about?
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5. HEXAWAT?
   Who is this crazy person?
   What is he talking about?
   Why is the rum gone?
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6. HEXAGONAL
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7. HEXAGONAL
   Hexagonal Architecture
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8. HEXAGONAL
   Hexagonal Architecture
   Describes the structure of an app
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9. HISTORY
   Originally by Alistair Cockburn
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10. HISTORY
    Originally by Alistair Cockburn
    Also called “Ports and Adaptors”
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11. HISTORY
    Back in t’day
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12. HISTORY
    Back in t’day
    3 Layer Architecture
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13. HISTORY
    Back in t’day
    3 Layer Architecture
    GUI => Logic => DB
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14. Application
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15. HEXAGONAL
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16. HEXAGONAL
    Decouple the application
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17. HEXAGONAL
    Decouple the application
    Make the business logic the focus
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18. HEXAGONAL
    Decouple the application
    Make the business logic the focus
    Provide adaptors for technology
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19. HEXAGONAL
    Decouple the application
    Make the business logic the focus
    Provide adaptors for technology
    Provide adaptors for I/O
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20. HEXAGONAL RAILS
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21. HEXAGONAL RAILS
    Describes structure of application
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22. HEXAGONAL RAILS
    Describes structure of application
    but... Rails is not the application
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23. HEXAGONAL RAILS
    Describes structure of application
    but... Rails is not the application
    ... Rails is the HTTP Adaptor
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24. HEXAGONAL RAILS
    Describes building apps *with* Rails
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25. Application
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26. RAILS
    CMD
    LINE
    LOGGING
    DB
    Application
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27. WHY?
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28. WHY?
    Separate responsibilities
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29. WHY?
    Separate responsibilities
    Not just SOC
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30. WHY?
    Separate responsibilities
    Not just SOC
    Separate business logic from web logic
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31. WHY?
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32. WHY?
    Push dependencies inwards
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33. WHY?
    Push dependencies inwards
    Make things more explicit
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34. WHY?
    Push dependencies inwards
    Make things more explicit
    Easier to see coupling / dependancies
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35. WHY?
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36. WHY?
    Modular code
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37. WHY?
    Modular code
    Isolated / Testable code
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38. WHY?
    Modular code
    Isolated / Testable code
    Cleaner code
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39. INTERLUDE
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40. HOW?
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41. HOW?
    Dependency Injection / Inversion
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42. HOW?
    Dependency Injection / Inversion
    Pure Ruby service classes
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43. HOW?
    Dependency Injection / Inversion
    Pure Ruby service classes
    Define an API / Duck Typing
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44. CONTROLLERS
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45. CONTROLLERS
    Controller provides what is needed
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46. CONTROLLERS
    Controller provides what is needed
    Controller provides how to respond
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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
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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
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49. RESPONDERS
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50. RESPONDERS
    Wrap response logic
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51. RESPONDERS
    Wrap response logic
    Can be reused
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52. RESPONDERS
    Wrap response logic
    Can be reused
    Can be stacked
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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
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54. CORE
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55. CORE
    Do things without knowledge of Rails
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56. CORE
    Do things without knowledge of Rails
    Respond back with results
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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
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58. DEPENDENCY INJECTION
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59. DEPENDENCY INJECTION
    Not scary
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60. DEPENDENCY INJECTION
    Not scary
    Can be simple plain Ruby
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61. DEPENDENCY INJECTION
    Not scary
    Can be simple plain Ruby
    Pass in what you need
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62. SIDE NOTE
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63. SIDE NOTE
    Use Rack, Use Routes
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64. SIDE NOTE
    Use Rack, Use Routes
    Provide info before the controller
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65. SIDE NOTE
    Use Rack, Use Routes
    Provide info before the controller
    E.g. Warden / Rack env for users.
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66. PERSISTENCE
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67. PERSISTENCE
    Not very talked about
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68. PERSISTENCE
    Not very talked about
    No consensus
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69. PERSISTENCE
    Not very talked about
    No consensus
    Still hard, how do we deal with AR?
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70. PERSISTENCE
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71. PERSISTENCE
    Wrap ORM API
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72. PERSISTENCE
    Wrap ORM API
    Create repositories that pass back
    objects
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73. PERSISTENCE
    Wrap ORM API
    Create repositories that pass back
    objects
    Use DataMapper pattern?
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74. TOOLS
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75. TOOLS
    What can we use to streamline this?
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76. OBJECTIFY
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77. OBJECTIFY
    Not strictly Hexagonal
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78. OBJECTIFY
    Not strictly Hexagonal
    Request Execution Framework
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79. OBJECTIFY
    Not strictly Hexagonal
    Request Execution Framework
    Dependency Injection aka Raptor
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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
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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
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82. MORPHINE
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83. MORPHINE
    Lightweight DI tool
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84. class Application
    include Morphine
    register :service do
    Service.new client
    end
    def perform_action(client)
    service.authorize!
    end
    end
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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
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86. PERPETUITY
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87. PERPETUITY
    DataMapper implementation
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88. PERPETUITY
    DataMapper implementation
    Define mappers for PORO Objects
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89. PERPETUITY
    DataMapper implementation
    Define mappers for PORO Objects
    Would probably still need a wrapper
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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
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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]
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92. SUMMARY
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93. SUMMARY
    Push / Inject dependencies
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94. SUMMARY
    Push / Inject dependencies
    Give application logic ways to respond
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95. SUMMARY
    Push / Inject dependencies
    Give application logic ways to respond
    Isolate components
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96. SUMMARY
    Push / Inject dependencies
    Give application logic ways to respond
    Isolate components
    Define *your* API
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97. BENEFITS
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98. BENEFITS
    Cleaner code
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99. BENEFITS
    Cleaner code
    Faster tests
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100. BENEFITS
     Cleaner code
     Faster tests
     Easier to adapt
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101. THANKS
     Jon Rowe
     @jonrowe (Twitter, GitHub, etc)
     http://jonrowe.co.uk
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102. LINKS
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103. LINKS
     https://github.com/bitlove/objectify
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104. LINKS
     https://github.com/bitlove/objectify
     https://github.com/bkeepers/morphine
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105. LINKS
     https://github.com/bitlove/objectify
     https://github.com/bkeepers/morphine
     https://github.com/jgaskins/perpetuity
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106. LINKS
     https://github.com/bitlove/objectify
     https://github.com/bkeepers/morphine
     https://github.com/jgaskins/perpetuity
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107. LINKS
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108. LINKS
     http://weblog.therealadam.com/
     2011/10/09/your-frienemy-the-orm/
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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/
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