NestJS - 如何自我引用 mongoDB 架构 @nestjs/mongoose？

Posted 2023-03-11

【中文标题】NestJS - 如何自我引用 mongoDB 架构 @nestjs/mongoose？

【英文标题】：NestJS - How to self reference a mongoDB Schema @nestjs/mongoose?

【发布时间】：2021-06-28 07:53:41

【问题描述】：

我正在尝试使用 @nestjs/mongoose 包自引用 Checklist 架构。但它抛出了一个 ReferenceError。我花了几个小时寻找解决方案，但一无所获，如果有人知道自我参考的正确方法，请帮助我...

错误

ReferenceError: Cannot access 'Checklist' before initialization
    at Object.<anonymous> (/home/farhantahir/Projects/bonsai-backend-api/dist/db/checklists/checklists.schema.js:24:31)
    at Module._compile (internal/modules/cjs/loader.js:1176:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1196:10)
    at Module.load (internal/modules/cjs/loader.js:1040:32)
    at Function.Module._load (internal/modules/cjs/loader.js:929:14)
    at Module.require (internal/modules/cjs/loader.js:1080:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at Object.<anonymous> (/home/farhantahir/Projects/bonsai-backend-api/dist/db/checklists/index.js:13:14)
    at Module._compile (internal/modules/cjs/loader.js:1176:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1196:10)
    at Module.load (internal/modules/cjs/loader.js:1040:32)
    at Function.Module._load (internal/modules/cjs/loader.js:929:14)
    at Module.require (internal/modules/cjs/loader.js:1080:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at Object.<anonymous> (/home/farhantahir/Projects/bonsai-backend-api/dist/db/index.js:14:14)
    at Module._compile (internal/modules/cjs/loader.js:1176:30)

这是我的架构

import * as mongoose from "mongoose"
import  Prop, Schema, SchemaFactory  from "@nestjs/mongoose"
import shortid from "shortid"

import 
  CHECKLIST_VISIBILITY,
  CHECKLIST_VISIBILITY_UNLISTED,
 from "~common/constants"
import  BaseItem  from "../common/schemas/BaseItem"
import  descriptionLengthValidation  from "../validators"
import  User  from "../users"

export type ChecklistVisibility = "public" | "private" | "unlisted"
export type ChecklistItemDocument = ChecklistItem & mongoose.Document
export type ChecklistDocument = Checklist & mongoose.Document

@Schema( timestamps: true )
class ChecklistItem extends BaseItem 
  @Prop( type: mongoose.Schema.Types.ObjectId, ref: "Checklist" )
  linkedList: Checklist


@Schema()
export class Subscriber 
  @Prop( type: mongoose.Schema.Types.ObjectId, ref: "User" )
  user: User

  @Prop( type: mongoose.Schema.Types.ObjectId, ref: "Checklist" )
  subscribedChecklist


@Schema( timestamps: true )
export class Checklist 
  @Prop(
    validate: descriptionLengthValidation,
  )
  description: string

  @Prop( trim: true )
  name: string

  @Prop( type: mongoose.Schema.Types.ObjectId, ref: "Checklist" )
  parent: Checklist    // <== Self Reference

  @Prop( default: shortid.generate, permanent: true, unique: true )
  slug: string

  @Prop( type: mongoose.Schema.Types.ObjectId, ref: "User" )
  user: User

  @Prop( default: CHECKLIST_VISIBILITY_UNLISTED, enum: CHECKLIST_VISIBILITY )
  visibility: string

  @Prop(
    type: mongoose.Schema.Types.ObjectId,
    ref: "Checklist",
  )
  subscribedFrom: Checklist      // <== Self Reference

  @Prop()
  subscribedAt: Date

  @Prop()
  subscribers: [Subscriber]

  @Prop()
  items: [ChecklistItem]

  @Prop()
  trashedAt: Date


export const ChecklistSchema = SchemaFactory.createForClass(Checklist)

ChecklistSchema.pre("find", function () 
  this.where( trashedAt:  $exists: false  )
)

【参考方案1】：

您将 Checklist 用于订阅者类，当时尚未声明 Checklist 类。你应该先声明 Checklist 类。