टाइपस्क्रिप्ट के साथ शुद्ध वास्तुकला: डीडीडी और स्तरित वास्तुकला

परिचय

DDD क्यों?

क्यों स्तरित वास्तुकला?

आर्किटेक्चर

इस सरल आवेदन के लिए ...

डोमेन

export abstract class Entity<T> {
  protected readonly _id: string
  protected props: T

  constructor(props: T, id?: string) {
    this._id = id ? id : UniqueEntityID()
    this.props = props
  }

  // other common methods here...
}

export class Cart extends Entity<ICartProps> {
  private constructor({ id, ...data }: ICartProps) {
    super(data, id)
  }

  public static create(props: ICartProps): Cart {
    const instance = new Cart(props)
    return instance
  }

  public unmarshal(): UnmarshalledCart {
    return {
      id: this.id,
      products: this.products.map(product => ({
        item: product.item.unmarshal(),
        quantity: product.quantity
      })),
      totalPrice: this.totalPrice
    }
  }

  private static validQuantity(quantity: number) {
    return quantity >= 1 && quantity <= 1000
  }

  private setProducts(products: CartItem[]) {
    this.props.products = products
  }

  get id(): string {
    return this._id
  }

  get products(): CartItem[] {
    return this.props.products
  }

  get totalPrice(): number {
    const cartSum = (acc: number, product: CartItem) => {
      return acc + product.item.price * product.quantity
    }

    return this.products.reduce(cartSum, 0)
  }

  public add(item: Item, quantity: number) {
    if (!Cart.validQuantity(quantity)) {
      throw new ValidationError(
        'SKU needs to have a quantity between 1 and 1000'
      )
    }

    const index = this.products.findIndex(
      product => product.item.sku === item.sku
    )

    if (index > -1) {
      const product = {
        ...this.products[index],
        quantity: this.products[index].quantity + quantity
      }

      if (!Cart.validQuantity(product.quantity)) {
        throw new ValidationError('SKU exceeded allowed quantity')
      }

      const products = [
        ...this.products.slice(0, index),
        product,
        ...this.products.slice(index + 1)
      ]

      return this.setProducts(products)
    }

    const products = [...this.products, { item, quantity }]
    this.setProducts(products)
  }

  public remove(itemId: string) {
    const products = this.products.filter(product => product.item.id !== itemId)
    this.setProducts(products)
    this.emitCartMutation()
  }

  public empty() {
    this.setProducts([])
  }
}

उपयोगकर्ता स्क्रिप्ट

import { inject, injectable } from 'inversify'

@injectable()
export class CartService {
  @inject(TYPES.CartRepository) private repository: CartRepository

  private async _getCart(id: string): Promise<Cart> {
    try {
      const cart = await this.repository.getById(id)
      return cart
    } catch (e) {
      const emptyCart = Cart.create({ id, products: [] })
      return this.repository.create(emptyCart)
    }
  }

  public getById(id: string): Promise<Cart> {
    return this.repository.getById(id)
  }

  public async add(cartId: string, item: Item, sku: number): Promise<Cart> {
    const cart = await this._getCart(cartId)
    cart.add(item, sku)

    return this.repository.update(cart)
  }

  public async remove(cartId: string, itemId: string): Promise<Cart> {
    const cart = await this._getCart(cartId)
    cart.remove(itemId)

    return this.repository.update(cart)
  }
}

भूमिकारूप व्यवस्था

import { Cart, CartItem } from 'src/domain/cart'

const getProducts = (products: CartItem[]) => {
  return products.map(product => ({
    item: product.item,
    quantity: product.quantity
  }))
}

export class CartMapper {
  public static toDomain(raw: any): Cart {
    return Cart.create({
      id: raw.id,
      couponCode: raw.couponCode,
      products: getProducts(raw.products || [])
    })
  }
}

import { injectable, inject } from 'inversify'
import { Cart } from 'src/domain/cart'
import { CartMapper } from '../mappers/cart'

interface ICartRepository {
  getById(id: string): Promise<Cart>
  create(cart: Cart): Promise<Cart>
  update(cart: Cart): Promise<Cart>
}

@injectable()
export class CartRepository implements ICartRepository {
  @inject(TYPES.Database) private _database: MemoryData

  async getById(id: string): Promise<Cart> {
    const cart = await this._database.cart.getById(id)
    if (!cart) {
      throw new ResourceNotFound('Cart', { id })
    }
    return CartMapper.toDomain(cart)
  }

  async create(cart: Cart): Promise<Cart> {
    const dtoCart = cart.unmarshal()
    const inserted = await this._database.cart.insert(dtoCart)
    return CartMapper.toDomain(inserted)
  }

  async update(cart: Cart): Promise<Cart> {
    const dtoCart = cart.unmarshal()
    const updated = await this._database.cart.update(cart.id, dtoCart)
    return CartMapper.toDomain(updated)
  }
}

निष्कर्ष