我按照 此处 所述设置了一个 Nest.Js / TypeORM / MongoDB 堆栈。

使用 create() 函数在 MongoDB 中创建对象用户是可行的，该对象被记录到正确的数据库的 User 集合中。

但是，当我尝试使用 find({id}) 或 findAll() 函数获取它时，出现错误，即使它在那里，我也无法从数据库中获取该项目。

这是我的 user.service.ts 文件：

import { Injectable, HttpException, HttpStatus } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { MongoRepository } from 'typeorm';
import { validate } from 'class-validator';
import { CreateUserDto } from './user.dto';
import { User } from '../model/user.entity';
import { UserRO } from './user.interface';

@Injectable()
export class UserService {
  constructor(
    @InjectRepository(User)
    private readonly userRepository: MongoRepository<User>,
  ) {}

  // abstracting access to the model via service
  public async getAll() {
    // getting data from database
    return await this.userRepository.find();
  }

  // abstracting access to the model via service
  public async get(id: string) {
    const user = await this.userRepository.findOne({ _id: id });
    if (!user) {
      const errors = { User: ' not found' };
      throw new HttpException({ errors }, 401);
    }

    return this.buildUserRO(user);
  }



  async create(dto: CreateUserDto): Promise<UserRO> {
    // check uniqueness of username/email
    const { username } = dto;
    const newUser = new User();
    newUser.username = username;
    // newUser.contexts = [];

    const errors = await validate(newUser);
    if (errors.length > 0) {
      const _errors = { username: 'Userinput is not valid.' };
      throw new HttpException(
        { message: 'Input data validation failed', _errors },
        HttpStatus.BAD_REQUEST,
      );
    } else {
      const savedUser = await this.userRepository.save(newUser);
      return this.buildUserRO(savedUser);
    }
  }


}

和还有 user.interface.ts :

export interface UserData {
  username: string;
  _id: string;
}

// user response object
export interface UserRO {
  user: UserData;
}

以及 user.controller.ts 的一部分:

  @Get(':id')
  findOne(@Param('id') id: string): Promise<UserRO> {
    console.log(`getting user with id: ${id}`);
    const user = this.serv.get(id);
    return user;
  }

最后是 model/user.entity.ts :

@Entity({ name: 'User' })
export class User {
  @ObjectIdColumn()
  _id: string;

  @Column({ type: 'varchar', length: 50 })
  username: string;

  @OneToMany((type) => Context, (context) => context.user)
  contexts: Context[];
}

当我尝试查找已保存的上下文时收到的错误:

[Nest] 75671  - 09/22/2021, 9:22:18 PM   ERROR [ExceptionsHandler] Cannot read property 'prototype' of undefined
TypeError: Cannot read property 'prototype' of undefined
    at FindCursor.cursor.toArray (/Users/deemeetree/Documents/Root/benchmark-sql-graph/src/entity-manager/MongoEntityManager.ts:707:37)
    at MongoEntityManager.<anonymous> (/Users/deemeetree/Documents/Root/benchmark-sql-graph/src/entity-manager/MongoEntityManager.ts:190:46)
    at step (/Users/deemeetree/Documents/Root/benchmark-sql-graph/node_modules/typeorm/node_modules/tslib/tslib.js:143:27)
    at Object.next (/Users/deemeetree/Documents/Root/benchmark-sql-graph/node_modules/typeorm/node_modules/tslib/tslib.js:124:57)
    at fulfilled (/Users/deemeetree/Documents/Root/benchmark-sql-graph/node_modules/typeorm/node_modules/tslib/tslib.js:114:62)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)

我尝试使用 MongoDB 4. 和 3. 版本，但问题相同。

我做错了什么，如何解决此错误并能够在 MongoDB 中很好地查询记录？

谢谢！