Validate nested objects using class validator and nestjs

Question

I'm trying to validate nested objects using class-validator and NestJS. I've already tried following this thread by using the @Type decorator from class-transform and didn't have any luck. This what I have:

DTO:

class PositionDto {
  @IsNumber()
  cost: number;

  @IsNumber()
  quantity: number;
}

export class FreeAgentsCreateEventDto {

  @IsNumber()
  eventId: number;

  @IsEnum(FinderGamesSkillLevel)
  skillLevel: FinderGamesSkillLevel;

  @ValidateNested({ each: true })
  @Type(() => PositionDto)
  positions: PositionDto[];

}

I'm also using built-in nestjs validation pipe, this is my bootstrap:

async function bootstrap() {
  const app = await NestFactory.create(ServerModule);
  app.useGlobalPipes(new ValidationPipe());
  await app.listen(config.PORT);
}
bootstrap();

It's working fine for other properties, the array of objects is the only one not working.

I've just put your code in an empty sample project and it seems to work for me. What specific value is "not working"? What are your expectations? If you for example put "positions": [{"other": true}] in your body it rejects with 400. positions: [] is a valid value though. — Kim Kern
– Kim Kern, Commented Dec 14, 2018 at 20:35
I'm expecting that if you try positions: [1], it throws an error — Leonardo Emilio Dominguez
– Leonardo Emilio Dominguez, Commented Dec 14, 2018 at 20:37
2023 and people still using this library... Thanks for question and answers! — fider
– fider, Commented Sep 26, 2023 at 13:26

tarek noaman · Accepted Answer · 2020-07-19 19:39:20Z

104

for me, I would able to validate nested object with 'class-transformer'

import { Type } from 'class-transformer';

full example:

import {
  MinLength,
  MaxLength,
  IsNotEmpty,
  ValidateNested,
  IsDefined,
  IsNotEmptyObject,
  IsObject,
  IsString,
} from 'class-validator';
import { Type } from 'class-transformer';

class MultiLanguageDTO {
  @IsString()
  @IsNotEmpty()
  @MinLength(4)
  @MaxLength(40)
  en: string;

  @IsString()
  @IsNotEmpty()
  @MinLength(4)
  @MaxLength(40)
  ar: string;
}

export class VideoDTO {
  @IsDefined()
  @IsNotEmptyObject()
  @IsObject()
  @ValidateNested()
  @Type(() => MultiLanguageDTO)
  name!: MultiLanguageDTO;
}

answered Jul 19, 2020 at 19:39

tarek noaman

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2 Comments

snehanshu.js Over a year ago

Use class-transformer-validator to validate it easily.

IB3N Over a year ago

Why have you used the "!" on VideoDTO.name here?

Kim Kern · Accepted Answer · 2018-12-14 21:16:09Z

44

You are expecting positions: [1] to throw a 400 but instead it is accepted.

According to this Github issue, this seems to be a bug in class-validator. If you pass in a primitive type (boolean, string, number,...) or an array instead of an object, it will accept the input as valid although it shouldn't.

I don't see any standard workaround besides creating a custom validation decorator:

import { registerDecorator, ValidationOptions, ValidationArguments } from 'class-validator';

export function IsNonPrimitiveArray(validationOptions?: ValidationOptions) {
  return (object: any, propertyName: string) => {
    registerDecorator({
      name: 'IsNonPrimitiveArray',
      target: object.constructor,
      propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {
          return Array.isArray(value) && value.reduce((a, b) => a && typeof b === 'object' && !Array.isArray(b), true);
        },
      },
    });
  };
}

and then use it in your dto class:

@ValidateNested({ each: true })
@IsNonPrimitiveArray()
@Type(() => PositionDto)
positions: PositionDto[];

edited Dec 14, 2018 at 21:16

answered Dec 14, 2018 at 21:09

Kim Kern

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2 Comments

Adora González Over a year ago

Is this supposed to transform each element of positions to PositionDto with its internal elements? If not, how can it be achieved, or do I necessarily have to do the transformations manually?

Kim Kern Over a year ago

@AdrianGonzález Check this answer for nested validation/transformation: stackoverflow.com/a/53685045/4694994

Vansham Aggarwal · Accepted Answer · 2021-11-18 04:24:57Z

3

I faced the same issue, so I created my own ValidateNested decorator.

import {
  ValidationOptions,
  registerDecorator,
  ValidationArguments,
  validateSync,
} from 'class-validator';
import { plainToClass } from 'class-transformer';

/**
 * @decorator
 * @description A custom decorator to validate a validation-schema within a validation schema upload N levels
 * @param schema The validation Class
 */
export function ValidateNested(
  schema: new () => any,
  validationOptions?: ValidationOptions
) {
  return function (object: Object, propertyName: string) {
    registerDecorator({
      name: 'ValidateNested',
      target: object.constructor,
      propertyName: propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {
          args.value;
          if (Array.isArray(value)) {
            for (let i = 0; i < (<Array<any>>value).length; i++) {
              if (validateSync(plainToClass(schema, value[i])).length) {
                return false;
              }
            }
            return true;
          } else
            return validateSync(plainToClass(schema, value)).length
              ? false
              : true;
        },
        defaultMessage(args) {
          if (Array.isArray(args.value)) {
            for (let i = 0; i < (<Array<any>>args.value).length; i++) {
              return (
                `${args.property}::index${i} -> ` +
                validateSync(plainToClass(schema, args.value[i]))
                  .map((e) => e.constraints)
                  .reduce((acc, next) => acc.concat(Object.values(next)), [])
              ).toString();
            }
          } else
            return (
              `${args.property}: ` +
              validateSync(plainToClass(schema, args.value))
                .map((e) => e.constraints)
                .reduce((acc, next) => acc.concat(Object.values(next)), [])
            ).toString();
        },
      },
    });
  };
}

Then you can use it like -

class Schema2 {

  @IsNotEmpty()
  @IsString()
  prop1: string;

  @IsNotEmpty()
  @IsString()
  prop2: string;
}


class Schema1 {
  @IsNotEmpty()
  @IsString()
  prop3: string;

  @ValidateNested(Schema2)
  nested_prop: Schema2;
}

Works for both non-primitive arrays and javascript objects.

answered Nov 18, 2021 at 4:24

Vansham Aggarwal

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2 Comments

Ahmed Over a year ago

I don't the @ValidateNested(Schema2) is still valid with the current version of class-validator v0.14.0

olawalejuwonm Over a year ago

Thank you this worked. But i'm getting some typing issue Type '(args: ValidationArguments | undefined) => string | undefined' is not assignable to type '(validationArguments?: ValidationArguments | undefined) => string'. Type 'string | undefined' is not assignable to type 'string'. Type 'undefined' is not assignable to type 'string'. No overload matches this call. Overload 1 of 2, '(o: { [s: string]: string; } | ArrayLike<string>): string[]', gave the following error. Argument of type '{ [type: string]: string; } | undefined' is not assignable to

Friday Onojah · Accepted Answer · 2024-10-17 21:46:24Z

1

I had same problem but got it fixed by doing:

import {
 ValidateNested,
 IsDefined,
 IsNotEmptyObject,
} from 'class-validator';

import { Type } from 'class-transformer';
import { ApiProperty } from '@nestjs/swagger';

@IsDefined()
@IsNotEmptyObject()
@ValidateNested()
@ApiProperty()
@Type(() => AddressDto)
address: AddressDto;

Using this answer stackoverflow.com/a/53685045/4694994

answered Oct 17, 2024 at 21:46

Friday Onojah

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