loopback 4 如何避免在购物车中创建超过 5 件商品

Question

我是 loopback 4 的新手，我找到的几乎所有文档都是针对低版本的。我有一个购物车，但我需要避免它有超过 5 件商品...我该如何进行此约束？

这些是我的模型：

import {Entity, hasMany, model, property} from '@loopback/repository';
import {Item} from './item.model';

@model()
export class Shoppingcar extends Entity {
  @property({
    type: 'string',
    id: true,
    generated: true,
  })
  id?: string;

  @property({
    type: 'string',
    required: true,
  })
  desc: string;

  @property({
    type: 'string',
    required: true,
    }
  })
  shopper: string;

  @hasMany(() => Item)
  items: Item[];

  constructor(data?: Partial<Gateway>) {
    super(data);
  }
}

export interface ShoppingcarRelations {
  // describe navigational properties here
}

export type ShoppingcarWithRelations = Shoppingcar & ShoppingcarRelations;

和

import {Entity, model, property, belongsTo} from '@loopback/repository';
import {Shoppingcar} from './shoppingcar.model';

@model()
export class Item extends Entity {
  @property({
    type: 'string',
    id: true,
    generated: true,
  })
  id?: string;

  @property({
    type: 'string',
    required: true,
  })
  name: string;

  @property({
    type: 'string',
    required: true,
  })
  date: string;

  @belongsTo(() => Shoppingcar)
  shoppingcarId: string;

  constructor(data?: Partial<Item>) {
    super(data);
  }
}

export interface ItemRelations {
  // describe navigational properties here
}

export type ItemWithRelations = Item & ItemRelations;

Answer 1

创建一个拦截器，检查拦截器中的项目计数，如果计数大于 5 则抛出错误，否则继续 next()

loopback 4 如何避免在购物车中创建超过 5 件商品

loopback 4 how to avoid creating more than 5 items in a shopping cart

constraints

loopback4