NestJS + Mongoose + GraphQL : “populate” not working

Question

thanks for the great framework!

I use mongoose with GraphQL and have the following problem:

If I want to resolve the ObjectIDs stored in the array "arguments" of a user with populate , in GraphQL I get the user with an empty arguments array as answer.

I suspect the error when defining the reference ArgumentSchema (name of the MongoDB schema) or the populate arguments (name of the attributes of the user). How does this work correctly?

argument.schema

export const ArgumentSchema = new mongoose.Schema({
  argument: { type: String, required: true },
  userId: { type: String, required: true },
  username: { type: String, required: true },
});

user.schema

export const UserSchema = new mongoose.Schema({
  username: { type: String, required: true },
  email: { type: String, required: true },
  age: { type: Number, required: true },
  arguments: { type: [mongoose.Schema.Types.ObjectId], required: false, ref: 'ArgumentSchema' },
});

argument.model

@ObjectType()
export class ArgumentGQL {
  @Field(() => ID)
  readonly _id: string;

  @Field()
  readonly argument: string;

  @Field()
  readonly userId: string;

  @Field()
  readonly username: string;
}

user.model

@ObjectType()
export class UserGQL {
  @Field(() => ID)
  readonly _id: string;

  @Field()
  readonly username: string;

  @Field()
  readonly email: string;

  @Field()
  readonly age: number;

  @Field(() => [ArgumentGQL], { nullable: true })
  readonly arguments: ArgumentGQL[];
}

user.service

async getOne(id: string): Promise<UserGQL> {
    try {
      return await this.userModel.findById(id).populate('arguments').exec();
    } catch (e) {
      throw new BadRequestException(e);
    }
  }

GraphlQL Query example

query {
  getUser(id: "5dbcaf9f5ba1eb2de93a9301") {
      _id,
      username,
      email,
      age,
      arguments {
          argument,
          username
      }
  }
}

I think I haven't understood something fundamental yet...

I would be grateful for any help! Cheers

Answer 1

I guess the problem, maybe is the way you defined user.schema . As It mentioned here , have you tried this?

{
 arguments: [{ type: [mongoose.Schema.Types.ObjectId], , ref: 'ArgumentSchema' }],
}