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

Question

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 } })
})

Answer 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。