MOPCON 2022 - 從 Domain-Driven Design 看網站開發框架隱藏

Domain-Driven Design 在近年是經常被討論的一種系統設計的方式，在學習思考方式的過程中，意外的發現在實作上有許多地方可以解釋我們在使用網站開發框架時無法清晰解釋的細節。

以 Ruby on Rails 經常被濫用的 Service Object 為例子，從 Domain-Driven Design 角度的思考，實際上就是 Domain Service 的角色，該在怎樣的時機使用、該封裝怎樣的內容馬上就變得明確。

讓我們試著以 Domain-Driven Design 的戰術（程式實作）來分析網站開發框架將哪些細節簡化使我們得以容易入門，又開如何重新細化來對應不斷發展成更複雜的系統。

Transcript

1. 蒼時弦也 看網站開發框架 隠藏的細節 從Domain-Driven Design
2. CONSULTANT × SPEAKER 蒼時弦也 YouTube Coding Live Blog https://blog.aotoki.me Discord Discuss about Ruby Introduce About Me
3. What we talk about Overview The Layers The case study Why Domain-Driven Design Why Domain-Driven Design
4. What we talk about Overview The Layers The Layers The case study Why Domain-Driven Design
5. What we talk about Overview The Layers The case study The case study Why Domain-Driven Design
6. Opportunity Why Domain-Driven Design The Opportunity When I try to improve the code base
7. Framework and Design Why Domain-Driven Design Design Architecture Framework
8. Escape Why Domain-Driven Design Framework Ruby / PHP Framework Node.js / Golang Replace
9. Modeling Why Domain-Driven Design The Modeling From data to information
10. Modeling Why Domain-Driven Design Data State Action Modeling Change Object
11. Layered Architecture The Layers Layered Architecture Define the role of your "Class"
12. Presentation Layer The Layers Presentation Layer Transform between "data" and "object"
13. Presentation Layer The Layers Object @product.name Data <h1>Product</h1> Render Output (View) Rails View
14. Presentation Layer The Layers Object @product.name Data {"name": "Product"} Serialize Output (View) Rails View
15. Presentation Layer The Layers Data {"name":"Product"} Object params[:name] Deserialize Input (Param) Rails Controller
16. Application Layer The Layers Application Layer Define the flow of "action"
17. Application Layer The Layers Input User Flow Order.create! Payment.create! OrderMailer.confirmation
18. Application Layer The Layers Input User Flow Order.create! Payment.create! OrderMailer.confirmation Exception PaymentGatewayUnavailable Raise
19. Application Layer The Layers Input User Flow Order.create! Payment.create! OrderMailer.confirmation Input User Flow Order.find_or_create_by! Payment.create! OrderMailer.confirmation Idempotent
20. Domain Layer The Layers Domain Layer The "logic" related business
21. Domain Layer The Layers Period begin=2022-09-01, end=2022-10-31 Call in? 2022-09-30 Return true Value Object
22. Domain Layer The Layers Data State Action Modeling Change Entity
23. Domain Layer The Layers ShippingService#create_ticket!(order) if response.success? True order.shipping_id = response.id False raise ShippingProviderUnavailable Service Object
24. Infrastructure Layer The Layers Infrastructure Layer The way to interact with "data"
25. Infrastructure Layer The Layers PostgresOrderRepository implement IOrderRepository Write Read Orders Table Repository
26. Infrastructure Layer The Layers ShopifyOrderRepository implement IOrderRepository Call Shopify Order API Write Read Orders Table Repository
27. Testing The Layers Add Tests The reasonable way to test
28. Testing The Layers shipped.json.jbuilder ShippingController Order OrderRepository UserRepository Shipping ShippingRepository TicketRepository DHL::Client E2E Testing
29. Testing The Layers shipped.json.jbuilder ShippingController Order OrderRepository UserRepository Shipping ShippingRepository TicketRepository DHL::Client E2E Testing
30. Testing The Layers shipped.json.jbuilder ShippingController Order OrderRepository UserRepository Shipping ShippingRepository TicketRepository DHL::Client Unit Test
31. Testing The Layers shipped.json.jbuilder ShippingController Order OrderRepository UserRepository Shipping ShippingRepository TicketRepository DHL::Client Unit Test
32. Testing The Layers shipped.json.jbuilder ShippingController Order OrderRepository UserRepository Shipping ShippingRepository TicketRepository DHL::Client Workable Feature
33. Input Object Case Study Input Object How to "validate" the inputs
34. Input Object Case Study Input Profile @user.assign_attributes(params) @user.valid! @user.save!
35. Input Object Case Study Input Register @user = User.new(params) @user.valid! @user.save!
36. Input Object Case Study Input Register @form.valid! @user = User.new(@form.attributes) @user.save!
37. Input Object Case Study # Ruby on Rails validates :email, :password, presence: true validates :email, format: /\A[^@\s]+@[^@\s]+\z/ class RegisterForm include ActiveModel::API include ActiveModel::Validation attribute :email, :string attribute :password, :string end
38. Input Object Case Study # Ruby on Rails validates :email, :password, presence: true validates :email, format: /\A[^@\s]+@[^@\s]+\z/ class RegisterForm include ActiveModel::API include ActiveModel::Validation attribute :email, :string attribute :password, :string end validate :email_uniqueness
39. Input Object Case Study // NestJS class RegisterDto { email: string; password: string; } @IsEmail() @IsNotEmpty() @Post() @UsePipes(new ValidationPipe({ transform: true })) async create(@Body() registerDto: RegisterDto) { this.registrationService.create(registerDto); }
40. Input Object Case Study // NestJS @UsePipes(new ValidationPipe({ transform: true })) class RegisterDto { @IsEmail() email: string; @IsNotEmpty() password: string; } @Post() async create(@Body() registerDto: RegisterDto) { this.registrationService.create(registerDto); }
41. Input Object Case Study Input Steps Parse Request Validate DTO Dispatch Controller
42. Input Object Case Study // Pseudo Code function dispatch(request: HttpRequest) { controller, action = this.router.lookup(request.path) input = meta.inputs[action].build(request.params) controller[action].call(input) } meta = Reflect.getMeta(controller) validator = meta.validator[action] if (validator) { validator.validate(input) }
43. Error Handling Case Study Error Handling Where to fix the error?
44. Error Handling Case Study Input Order.create! Payment.create! OrderMailer.confirmation Exception PaymentGatewayUnavailable Raise
45. Error Handling Case Study # Ruby on Rails rescue PaymentGateWayUnavailable render :new class OrderController < ApplicationController def create @order = Order.create!(params) @payment = Payment.create!(order: @order) OrderMailer.confirmation(@order) end end
46. Error Handling Case Study # Ruby on Rails rescue PaymentGateWayUnavailable render :new class OrderController < ApplicationController def create @order = Order.create!(params) @payment = Payment.create!(order: @order) OrderMailer.confirmation(@order) end end rescue SomeErrorA # ... rescue SomeErrorB # ...
47. Error Handling Case Study # Ruby on Rails rescue_from ActiveRecord::ActiveRecordError, with: :record_error rescue_from PaymentService::PaymentError, with: :payment_error class OrderController < ApplicationController def create @order = Order.create!(params) @payment = Payment.create!(order: @order) OrderMailer.confirmation(@order) end end
48. Error Handling Case Study # Ruby on Rails @form = CreaetOrderForm.new(params) def payment_error(exc) @form.errors.add(:base, exc.message) render :new end class OrderController < ApplicationController rescue_from ActiveRecord::ActiveRecordError, with: :record_error rescue_from PaymentService::PaymentError, with: :payment_error def create # ... end end
49. Error Handling Case Study # Ruby on Rails module WithPaymentFlow # ... included do rescue_from PaymentService::PaymentError, with: :payment_flow_error end def payment_flow_error(exc) @form.errors.add(:base, exc.message) end end # response_with(@form)
50. Error Handling Case Study ActiveSupport::Rescuable ActionController ActionMailer ActionCable ActiveJob
51. Side Effect Case Study Side Effect Who changes my data?
52. Side Effect Case Study # Ruby on Rails class ShippingService # ... def refresh_shipping_state!(order, ticket) end end order.update( shipping_state: ticket.shipping_state, # ... )
53. Side Effect Case Study # Ruby on Rails class Merchant::ShippingController < ApplicationController # ... def update ticket = ShippingTicket.from_order!(@order) shipping_service.refresh_shipping_state!(@order, ticket) # ... @order.save! end end tracking_service.attach_event!(@order) #=> TrackingUnavailableError
54. Side Effect Case Study # Ruby on Rails class ShippingService # ... end def refresh_shipping_state(order, ticket) order.assign_attributes( shipping_state: ticket.shipping_state, # ... ) end
55. Side Effect Case Study # Ruby on Rails class Merchant::ShippingController < ApplicationController # ... def update # User Flow ticket = ShippingTicket.from_order!(@order) shipping_service.refresh_shipping_state(@order, ticket) tracking_service.attach_event!(@order) # Commit @order.save! end end # Input # ...
56. Side Effect Case Study # Ruby on Rails class Merchant::ShippingController < ApplicationController # ... def update # Input # ... # Commit @order.save! end end # User Flow ticket = ShippingTicket.from_order!(@order) shipping_service.refresh_shipping_state(@order, ticket) tracking_service.attach_event!(@order)
57. Side Effect Case Study # Ruby on Rails class Merchant::ShippingController < ApplicationController # ... def update # Input # ... # User Flow ticket = ShippingTicket.from_order!(@order) shipping_service.refresh_shipping_state(@order, ticket) tracking_service.attach_event!(@order) end end # Commit @order.save!
58. Value Object Case Study Value Object Manage logic in the "Domain Model"
59. Value Object Case Study # Ruby on Rails class Wallets::DepositController < ApplicationController def create # ... @wallet.save! end end @wallet.deposit(@form[‘amount’], @form[‘currency’])
60. Value Object Case Study # Ruby on Rails class Wallet < ApplicationRecord # ... def deposit(amount, currency) self.balance += amount end end raise CurrencyMismatch unless self.currency == currency
61. Value Object Case Study # Ruby on Rails class Wallet < ApplicationRecord # ... def deposit(amount) end end sig {params(amount: Money).returns(Money)} self.balance += amount
62. Value Object Case Study # Ruby on Rails class Money # ... end def +(other) raise ArgumentError, ‘...’ unless other.currency == currency Money.new(amount + other.amount, currency) end raise ArgumentError, ‘...’ unless other.is_a?(Money)
63. Value Object Case Study # Ruby on Rails class Wallet < ApplicationRecord # ... sig {params(amount: Money).returns(Money)} def deposit(amount) end end composed_of :balance, class_name: ‘Money’, mapping: [%i[balance amount], %i[currency currency]] self.balance += amount
64. Value Object Case Study # Ruby on Rails class Wallets::DepositController < ApplicationController def create # ... @wallet.save! end end @wallet.deposit(@form.amount)
65. Value Object Case Study # Ruby on Rails class Wallets::DepositController < ApplicationController def create # ... @wallet.save! end end @wallet.balance += @form.amount
66. Survey Feedback Survey https://www.surveycake.com/s/lboZ9