Nestjs class-validator nested object validation failure

Question

This is my model structure

import { Type } from "class-transformer"
import { IsObject, IsOptional, IsString, MaxLength, ValidateNested } from "class-validator"

export class DestinationRequest {
  @IsString()
  @MaxLength(2, { message: 'should be only of 2 letters' })
  lang: string

  @IsString()
  @MaxLength(50, { message: 'should be only of 50 letters' })
  name: string

  @IsOptional()
  @ValidateNested()
  @IsObject()
  @Type(() => AddressRequest)
  address: AddressRequest

  @IsString()
  @IsOptional()
  content: string
}


export class AddressRequest {
  @IsString()
  @MaxLength(50, { message: 'city should be only 50 letters' })
  city: string

  @IsString()
  @MaxLength(25, { message: 'country should be only 25 letters' })
  country: string

  @IsString()
  @IsOptional()
  @MaxLength(100, { message: 'detail should be only 100 letters' })
  detail: string

  @IsOptional()
  geolocation: {
    latitude: number,
    logitude: number
  }
}

When I run the app, the app fails to start with the following error

ReferenceError: Cannot access 'AddressRequest' before initialization at Object. (/destination.models.ts:17:12) at Module._compile (internal/modules/cjs/loader.js:1085:14) at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10) at Module.load (internal/modules/cjs/loader.js:950:32) at Function.Module._load (internal/modules/cjs/loader.js:790:12) at Module.require (internal/modules/cjs/loader.js:974:19) at require (internal/modules/cjs/helpers.js:101:18) at Object. () at Module._compile (internal/modules/cjs/loader.js:1085:14) at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)

Answer 1

The error is because the AddressRequest class has to be declared before DestinationRequest.

This fixed it for me

import { Type } from 'class-transformer';
import {
  IsObject,
  IsOptional,
  IsString,
  MaxLength,
  ValidateNested,
} from 'class-validator';

export class AddressRequest {
  @IsString()
  @MaxLength(50, { message: 'city should be only 50 letters' })
  city: string;

  @IsString()
  @MaxLength(25, { message: 'country should be only 25 letters' })
  country: string;

  @IsString()
  @IsOptional()
  @MaxLength(100, { message: 'detail should be only 100 letters' })
  detail: string;

  @IsOptional()
  geolocation: {
    latitude: number;
    logitude: number;
  };
}

export class DestinationRequest {
  @IsString()
  @MaxLength(2, { message: 'should be only of 2 letters' })
  lang: string;

  @IsString()
  @MaxLength(50, { message: 'should be only of 50 letters' })
  name: string;

  @IsOptional()
  @ValidateNested()
  @IsObject()
  @Type(() => AddressRequest)
  address: AddressRequest;

  @IsString()
  @IsOptional()
  content: string;
}