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Clean Architecture in Rails The way to large Rails application

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蒼時弦也 Software Developer https://blog.aotoki.me @elct9620

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Single Responsibility Dependency Injection Clean Architecture Clean Architecture in Rails

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Single Responsibility Dependency Injection Clean Architecture Clean Architecture in Rails

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Single Responsibility Dependency Injection Clean Architecture Clean Architecture in Rails

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Single Responsibility Dependency Injection Clean Architecture Clean Architecture in Rails

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Single Responsibility

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負責一件事情（ ） 關注點分離

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可能同時有多個功能（計算 + 讀寫）

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對系統切分的粒度

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class def end end ; Desk work

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class def end def = += end def = end def end end ; (amount ) @height amount (amount ); (slot); Desk work up down memory # Standing Desk # ... 1 1

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class def = end end
 class def = new
 end def = end
 end (amount ); @motor . (amount ) @motor.forward(amount) Motor
 forward Desk
 initialize up 1 Motor 1 # ... # ... # ...

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class def = end end
 (amount ); Motor
 forward 1 # ... class Desk
 def initialize @motor = Motor.new
 end # ... def up(amount=1) @motor.forward(amount) end
 # ... end

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class < def end private def end def end end ; ; ; CheckoutController ApplicationController create calculate_discount calculate_amount # ...

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class end class end class < def end end ; DiscountService CheckoutService CheckoutController ApplicationController create # ...

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class end class end DiscountService CheckoutService class CheckoutController < ApplicationController def create; end # ... end

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Dependency Injection

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由呼叫者提供依賴的物件或函式

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實踐 ，達到低耦合的程式 關注點分離

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在 Ruby 可以用 Duck Typing 方式實踐

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class def = end end
 class def = new
 end def = end
 end (amount ); @motor . (amount ) @motor.forward(amount) Motor
 forward Desk
 initialize up 1 Motor 1 # ... # ... # ...

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class def = end def = end
 end (motor) @motor motor
 (amount ) @motor.forward(amount) Desk
 initialize up # ... # ... 1

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class end class end = new new = new new ; ; @standing_desk . ( . ) @electrical_standing_desk . ( . ) Motor ElectricMotor # 手動 # 電動 Desk Motor Desk ElectricMotor

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class end class end class < def = new end end @discount . @discount.call(@order)
 DiscountService AnniversaryDiscountService CheckoutController ApplicationController create DiscountService # ... # ...

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class DiscountService end class AnniversaryDiscountService end class CheckoutController < ApplicationController def create @discount.call(@order)
 # ... end # ... end @discount . = new AnniversaryDiscountService

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class < def = end def = case when then new else new end end end @discount discount_service @discount.call(@order)
 @discount_service .current_store_event . . CheckoutController ApplicationController create discount_service # ... # ... Settings :anniversary AnniversaryDiscountService DiscountService

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Clean Architecture

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Architecture Framework Design 粗略 詳細 架構是從宏觀的角度觀察，設計則是從微觀的角度

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理想狀況 https://www.pinterest.com/pin/205687907955149475/

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現實狀況 https://knowyourmeme.com/photos/1624064-unfinished-horse-drawing-flaming-horse-rating

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區分出高階（抽象）跟低階（具體）元件

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# Which is highest?

 # ... # ... class def end end
 class def end end class < def = end end (amount, ); (order); @discount discount_service
 Order add_discount GeneralDiscountService call CheckoutController ApplicationController create reason:

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Controller Checkout Service Discount Entity Order 低階 高階 被越多物件引用的物件通常越高階（抽象）

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https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html

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越低階的物件越容易跟其他東西耦合

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class def end end class < def = end end class < def end end (text); res commander.call(...) client.reply(res) TextCommander call LineBotController ApplicationController callback MessengerBotController ApplicationController callback # ... # ...

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Clean Architecture 嘗試找出不同元件之間的邊界

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釐清邊界後，如何設計依賴、劃分模組就會有更清晰的方向

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Clean Architecture in Rails

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https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html

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Rails 的 Model、View、Controller 分別屬於哪一層？

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Controller Presenter Model Entity View Presenter Business Logic

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https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html Frameworks

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Model 適合當作 Business Logic 分類成 UseCase、Entity 嗎？

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Controller Controller Model Gateway View Presenter Rails 的 MVC 更可能是同層級的物件

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Framework Adapter + Business Logic MVC 框架的設計很容易把框架跟商業邏輯耦合在一起

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Service Object、Value Object 的出現是嘗試提煉商業邏輯

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Controller Controller Service UseCase View Presenter Business Logic

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我們將 Model 視為 Service 的依賴，注入給 Service 使用

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然而 Entity 不等於 Model，因為 ActiveRecord 跟底層細節耦合

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Controller Model View UseCase Entity

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class < def case in in end end end resolve( ).call(connect_params) => result render result.value, => result render result.failure, ConnectController ApplicationController create 'notify.connect' Success json: status: :created Failure json: status: :unprocessable_entity # ...

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module class < include private def end def ** = new end end end [ ] step try , :: :: (input) ( , , ) notify :: :: . ( token, type) notifies.save(notify) Notify Connect BaseOperation validate create Deps notifies: :validate :create catch: Notify Errors NotifyAlreadyExists token: type: Notify Entities Notify token: type: 'notify_repository' # ...

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module module class attr_reader def = = end end end end , ( , ) @token token @type type Notify Entities Notify initialize :token :type token: type: # ...

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# ActiveRecord model # API client class def = new end end class def end end (entity) notify . notify.assign_attributes(entity.to_h) notify.save! (entity) .upsert(entity.to_h) NotifyRepository save NotifyRepository save NotifyConnection NotifierAPI

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基於這樣的調整，除了擴充更容易外，我們也不再綁定框架

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以往難以判斷如何拆分物件、將商業邏輯提煉的線索更加清晰

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這是 Clean Architecture 應用的一小部分，還有許多面向可以發掘

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Question & Answer https://bit.ly/3YnmmQJ