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

蒼時弦也
看網站開發框架

隠藏的細節
從Domain-Driven

Design

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CONSULTANT × SPEAKER
蒼時弦也
YouTube Coding Live Blog https://blog.aotoki.me Discord Discuss about Ruby
Introduce About Me

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What we talk about Overview
The Layers
The case study
Why Domain-Driven Design

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The Layers
The Layers
The case study

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The Layers
The case study
The case study

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Opportunity Why Domain-Driven Design
The Opportunity
When I try to improve the code base

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Framework and Design Why Domain-Driven Design
Design
Architecture
Framework

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Escape Why Domain-Driven Design
Framework
Ruby / PHP
Framework
Node.js / Golang
Replace

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Modeling Why Domain-Driven Design
The Modeling
From data to information

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Modeling Why Domain-Driven Design
Data State Action
Modeling Change
Object

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Layered Architecture The Layers
Layered Architecture
Define the role of your "Class"

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Presentation Layer The Layers
Presentation Layer
Transform between "data" and "object"

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Object
@product.name
Data
Product
Render
Output (View)
Rails View

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Object
@product.name
Data
{"name": "Product"}
Serialize
Output (View)
Rails View

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Data
{"name":"Product"}
Object
params[:name]
Deserialize
Input (Param)
Rails Controller

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Application Layer The Layers
Application Layer
Define the flow of "action"

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Input
User Flow
Order.create!
Payment.create!
OrderMailer.confirmation

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Input
User Flow
Order.create!
Payment.create!
Exception
PaymentGatewayUnavailable
Raise

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Input
User Flow
Order.create!
Payment.create!
Input
User Flow
Order.find_or_create_by!
Payment.create!
Idempotent

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Domain Layer The Layers
Domain Layer
The "logic" related business

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Period
begin=2022-09-01, end=2022-10-31
Call in?
2022-09-30
Return true
Value Object

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Data State Action
Modeling Change
Entity

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ShippingService#create_ticket!(order)
if response.success?
True
order.shipping_id = response.id
False
raise ShippingProviderUnavailable
Service Object

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Infrastructure Layer The Layers
Infrastructure Layer
The way to interact with "data"

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PostgresOrderRepository
implement IOrderRepository
Write Read
Orders Table
Repository

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ShopifyOrderRepository
implement IOrderRepository
Call
Shopify Order API
Write Read
Orders Table
Repository

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Testing The Layers
Add Tests
The reasonable way to test

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Testing The Layers
shipped.json.jbuilder
ShippingController
Order
OrderRepository UserRepository
Shipping
ShippingRepository TicketRepository
DHL::Client
E2E Testing

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Testing The Layers
ShippingController
Order
Shipping
DHL::Client
Unit Test

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Testing The Layers
ShippingController
Order
Shipping
DHL::Client
Workable Feature

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Input Object Case Study
Input Object
How to "validate" the inputs

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Input
Profile
@user.assign_attributes(params)
@user.valid!
@user.save!

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Input
Register
@user = User.new(params)
@user.valid!
@user.save!

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Input
Register
@form.valid!
@user = User.new(@form.attributes)
@user.save!

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# 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

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# 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

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// NestJS

class RegisterDto {

email: string;

password: string;

}

@IsEmail()

@IsNotEmpty()

@Post()

@UsePipes(new ValidationPipe({ transform: true }))

async create(@Body() registerDto: RegisterDto) {

this.registrationService.create(registerDto);

}

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// NestJS

@UsePipes(new ValidationPipe({ transform: true }))

class RegisterDto {

@IsEmail()

email: string;

@IsNotEmpty()

password: string;

}

@Post()

async create(@Body() registerDto: RegisterDto) {

this.registrationService.create(registerDto);

}

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Input
Steps
Parse Request
Validate DTO
Dispatch Controller

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// 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)

}

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Error Handling Case Study
Error Handling
Where to fix the error?

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Input
Order.create!
Payment.create!
Exception
PaymentGatewayUnavailable
Raise

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# 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

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# Ruby on Rails

rescue PaymentGateWayUnavailable

render :new


def create




end

end
rescue SomeErrorA

# ...

rescue SomeErrorB

# ...

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# Ruby on Rails

rescue_from ActiveRecord::ActiveRecordError, with: :record_error

rescue_from PaymentService::PaymentError, with: :payment_error


def create




end

end

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# Ruby on Rails

@form = CreaetOrderForm.new(params)

def payment_error(exc)

@form.errors.add(:base, exc.message)

render :new

end


rescue_from ActiveRecord::ActiveRecordError, with: :record_error

rescue_from PaymentService::PaymentError, with: :payment_error

def create

# ...

end

end

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# 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)

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ActiveSupport::Rescuable
ActionController ActionMailer ActionCable ActiveJob

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Side Effect Case Study
Side Effect
Who changes my data?

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# Ruby on Rails

class ShippingService

# ...

def refresh_shipping_state!(order, ticket)

end

end
order.update(

shipping_state: ticket.shipping_state,

# ...

)

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# 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

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# Ruby on Rails

class ShippingService

# ...

end
def refresh_shipping_state(order, ticket)

order.assign_attributes(

shipping_state: ticket.shipping_state,

# ...

)

end

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# Ruby on Rails


# ...

def update

# User Flow


shipping_service.refresh_shipping_state(@order, ticket)

tracking_service.attach_event!(@order)

# Commit

@order.save!

end

end
# Input

# ...

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# Ruby on Rails


# ...

def update

# Input

# ...

# Commit

@order.save!

end

end
# User Flow




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# Ruby on Rails


# ...

def update

# Input

# ...

# User Flow




end

end
# Commit

@order.save!

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Value Object Case Study
Value Object
Manage logic in the "Domain Model"

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# Ruby on Rails

class Wallets::DepositController < ApplicationController

def create

# ...

@wallet.save!

end

end
@wallet.deposit(@form[‘amount’], @form[‘currency’])

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# Ruby on Rails

class Wallet < ApplicationRecord

# ...

def deposit(amount, currency)

self.balance += amount

end

end
raise CurrencyMismatch unless self.currency == currency

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# Ruby on Rails


# ...

def deposit(amount)

end

end
sig {params(amount: Money).returns(Money)}


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# 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)

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# Ruby on Rails


# ...

sig {params(amount: Money).returns(Money)}

def deposit(amount)

end

end
composed_of :balance,

class_name: ‘Money’,

mapping: [%i[balance amount], %i[currency currency]]


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# Ruby on Rails


def create

# ...

@wallet.save!

end

end
@wallet.deposit(@form.amount)

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# Ruby on Rails


def create

# ...

@wallet.save!

end

end
@wallet.balance += @form.amount

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Survey Feedback
Survey https://www.surveycake.com/s/lboZ9

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

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

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