question: await for promises when using class to plain

[vicdup]

Hi there, we are using class-transformer with groups in nestJs. We are struggling on how to make class-transformer await a property when this property is exposed. Currently it result in a null object.

For instance in our entity "Booking" we have a property "Contact" defined as follow:

class Example {
  @ManyToOne(type => Contact, contact => contact.bookings, { eager: true })
  @JoinColumn()
  @Expose({ groups: ['vero'] })
  @Field(type => Contact)
  contact: Promise<Contact>;
}

when we use plain to class on a booking fetched with "findOne" of Typeorm it results in :

contact: {}

[Petr0vi4]

Try to add Transform decorator:

@Transform(promise => promise.then(value => plainToClass(Contact, value)), { toClassOnly: true })

[vicdup]

Hi @Petr0vi4

I am not sure I understand your answer.

• we get a class "Booking" from our ORM (typeorm), "Booking" has a property "Contact" that is a promise and will resolve to a class "Contact" if awaited
• we send the Booking to ClassToPlain in order to get a js object
• the property Contact is serialized to an empty object and not awaited

Transform as you suggested does not work because it is not awaited and return a promise.

I feel like we are doing something wrong here because this seems so trivial...

[Petr0vi4]

You typed contact property as a Promise<Contact>, so I think that after plainToClass you should expect to receive a Promise, that will be resolved to object of class Contact if awaited.

[creaux]

Actually I feel this is similar kind of problem.

class SecondModel {
  @IsNumber()
  public get count(): Promise<number> {
    return promise.then((data) => data.count);
  }
}
....
class FirstModel {
  @IsDefined()
  @IsInstance(SecondModel, { each: true })
  @ValidateNested({ each: true })
  @Type(() => SecondModel)
  public readonly some!: SecondModel[];
}

I'm getting the following as result which point me on that the promise is note resolved.

firstModel.some === {} // which should be number of course

How to resolve that promise? It doesn't seem to me there is a way according documentation. Do I missing something?

[cosinus84]

@creaux did you find the solution to your problem, I ended in the same place.

[smecnarowski]

same for me - i'm trying to transform plaintext password to crypted string but i'm receiving it as empty object

import { IsString, IsEmail, IsBoolean, IsOptional, IsNotEmpty } from 'class-validator';
import { Transform } from 'class-transformer';
import * as bcrypt from 'bcrypt';

export class CreateUserDto {
  @IsEmail()
  @Transform(username => username.toLowerCase())
  readonly username: string;

  @IsString()
  @IsNotEmpty()
  @Transform(async password => {
    const hash = await bcrypt.hash(password, 10);
    return hash;
  })
  readonly password: string;

  @IsString()
  readonly name: string;

  @IsOptional()
  @IsBoolean()
  readonly isAdmin: boolean;

  @IsOptional()
  @IsBoolean()
  readonly isManufacturer: boolean;
}

[imSaharukh]

same for me - i'm trying to transform plaintext password to crypted string but i'm receiving it as empty object

import { IsString, IsEmail, IsBoolean, IsOptional, IsNotEmpty } from 'class-validator';
import { Transform } from 'class-transformer';
import * as bcrypt from 'bcrypt';

export class CreateUserDto {
  @IsEmail()
  @Transform(username => username.toLowerCase())
  readonly username: string;

  @IsString()
  @IsNotEmpty()
  @Transform(async password => {
    const hash = await bcrypt.hash(password, 10);
    return hash;
  })
  readonly password: string;

  @IsString()
  readonly name: string;

  @IsOptional()
  @IsBoolean()
  readonly isAdmin: boolean;

  @IsOptional()
  @IsBoolean()
  readonly isManufacturer: boolean;
}

did you find any solution? I'm facing the same issue

[namttdh]

same as me, both

@Transform(async avatar => {
   await stuff hrere...
    return avatar_str;
  })
 public avatar;

or

@Expose({name: 'avatar'})
  async getAvatar() {
    await something;
    return `${process.env.BASE_URL}/file/image/${this.avatar}/avatar.jpg`;
  }

doesn't work. Only return object empty {};

[smecnarowski]

@imSaharukh solved only by workaround. I have consulted on discord with developers and there were no solution for this because those transformations doesn't handle promise based solutions. Finally I inserted code to the service class

import { Injectable, Inject } from '@nestjs/common';
import * as bcrypt from 'bcrypt';
import { User } from './interfaces/user.interface';
import { Model } from 'mongoose';
import { CreateUserDto } from './dto/create-user.dto';

@Injectable()
export class UsersService {
  constructor(
    @Inject('USER_MODEL') 
    private userModel: Model<User>
  ) {}

  async create(createUserDto: CreateUserDto): Promise<User> {
    createUserDto.password = await bcrypt.hash(createUserDto.password, 10)
    const created = new this.userModel(createUserDto)
    return created.save()
  }

  ...

}

[iteratelance]

I have this same issue and have yet to find a workaround. This seems so basic and fundamental.

[NoNameProvided]

This is not possible currently, I have added a tracking issue for this feature at #549. Please do not comment +1, waiting for this comments on it. Comment only if you have to add something to the conversation. To express your interest, you can hit the like emote on the issue.

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