Powerful Interfaces

Transcript

1. Powerful Interfaces @caike RailsConf 2012

2. why developing Rails apps with fine-grained components is freaking awesome!

3. Granularity

4. Problems

5. Not Fun! http://www.flickr.com/photos/lianneviau/499003712/sizes/l/in/photostream/

6. Interface

7. class Payment < ActiveRecord::Base def complete end def cancel end

   end

8. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

   payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

9. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

   payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end Client

10. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end Client Interface

11. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

12. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

13. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end Coarse-Grained

14. Callbacks Observers

15. Three Laws of Interfaces

16. do what its methods say it does. #1

17. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

18. Payment#save vs. Payment#place

19. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

20. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

21. class Payment < ActiveRecord::Base protected :save ## # Add your

    comments here. # Really. Please do it :) ## def place end end

22. do no harm. #2

23. <h2>Registered Users</h2> <div class="users"> <ul> <% User.recent.paginate(@page).each do |user| %>

    <li><%= link_to(user.full_name, user) %></li> <% end %> </ul> </div>

24. <h2>Registered Users</h2> <div class="users"> <ul> <% User.recent.paginate(@page).each do |user| %>

    <li><%= link_to(user.full_name, user) %></li> <% end %> </ul> </div>

25. <h2>Registered Users</h2> <div class="users"> <ul> <% @users.each do |user| %>

    <li><%= link_to(user.full_name, user) %></li> <% end %> </ul> </div>

26. notify client if something goes wrong. #3

27. raise "Invalid HTTP request"

28. raise "Invalid HTTP request"

29. raise "Invalid HTTP request" vs. raise "PayX Authentication Error"

30. raise "PayX Authentication Error"

31. raise "PayX Authentication Error"

32. do what its methods say it does. #1

33. do no harm. #2

34. notify client if something goes wrong. #3

35. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

36. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

37. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

38. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end doing too much

39. Factory Method Pattern

40. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

41. class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if

    payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

42. class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if

    payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

43. class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if

    payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

44. class PlanSubscriber def self.build_for(user) end def subscribe(payment_info) end end

45. class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if

    payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

46. class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if

    payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

47. class PaymentsController < ApplicationController def create plan_subscriber = PlanSubscriber.build_for(current_user) if

    plan_subscriber.subscribe(params[:payment]) payment = plan_subscriber.payment redirect_to(payment, success:'You are now subscribed!') else render :index end end end

48. Design by Contract

49. Pre-Conditions Post-Conditions Invariants

50. Pre-Conditions

51. User must have a valid email address. Product must be

    available.

52. Pre-Conditions Post-Conditions

53. User must have a new payment. Seat must be reserved.

54. Pre-Conditions Post-Conditions Invariants

55. User must be registered. Store location must be open.

56. Pre-Conditions Post-Conditions Invariants

57. Fat models Thin controllers

58. Models != AR::Base

59. class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if

    payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

60. class PaymentsController < ApplicationController def create plan_subscriber = PlanSubscriber.build_for(current_user) if

    plan_subscriber.subscribe(params[:payment]) payment = plan_subscriber.payment redirect_to(payment, success:'You are now subscribed!') else render :index end end end

61. Rails is not your application http://blog.firsthand.ca/2011/10/rails-is-not-your- application.html

62. Extract your application into its own ruby gem.

63. None

64. http://objectsonrails.com

65. Rails Models Complexity Pyramid

66. 0 1 2 Rails Models Complexity Pyramid

67. 0 Rails out-of-the-box 1 2 Rails Models Complexity Pyramid

68. 0 Rails out-of-the-box 1 Protect AR::Base methods from controller 2

    Rails Models Complexity Pyramid

69. 0 2 Rails out-of-the-box Hide AR::Base classes from controller 1

    Protect AR::Base methods from controller Rails Models Complexity Pyramid

70. Thank you. @caike