Nested DTO validation in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the validation decorator for nested objects in NestJS.

NestJS

import { [1] } from 'class-validator';

Drag options to blanks, or click blank then click option'

AValidateNested

BIsString

CIsNumber

DIsNotEmpty

Attempts:

3 left

💡 Hint

Common Mistakes

Using IsString or IsNumber which validate primitive types, not nested objects.

The ValidateNested decorator is used to validate nested objects inside DTOs in NestJS.

2fill in blank

medium

Complete the code to apply nested validation on the 'address' property inside a DTO.

NestJS

export class UserDto {
  @[1]()
  address: AddressDto;
}

Drag options to blanks, or click blank then click option'

AIsNotEmpty

BIsString

CValidateNested

DIsArray

Attempts:

3 left

💡 Hint

Common Mistakes

Using IsString which only validates strings, not objects.

Forgetting to use ValidateNested for nested DTOs.

The ValidateNested decorator tells NestJS to validate the nested AddressDto object inside UserDto.

3fill in blank

hard

Fix the error in the code to ensure nested DTO validation works correctly with class-transformer.

NestJS

export class UserDto {
  @ValidateNested()
  @[1](() => AddressDto)
  address: AddressDto;
}

Drag options to blanks, or click blank then click option'

AType

BTransform

CExpose

DExclude

Attempts:

3 left

💡 Hint

Common Mistakes

Using Transform which is for custom transformations, not type hinting.

Omitting the Type decorator causes nested validation to fail.

The Type decorator from class-transformer is required to tell NestJS how to transform and validate nested objects.

4fill in blank

hard

Fill both blanks to define a nested DTO with validation decorators for its properties.

NestJS

export class AddressDto {
  @[1]()
  street: string;

  @[2]()
  city: string;
}

Drag options to blanks, or click blank then click option'

AIsString

BIsNumber

CIsNotEmpty

DIsBoolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using IsNumber or IsBoolean for string fields.

Forgetting to check that city is not empty.

IsString ensures the property is a string, and IsNotEmpty ensures it is not empty. Both are common validations for address fields.

5fill in blank

hard

Fill all three blanks to create a nested DTO with validation and type transformation.

NestJS

import { [1] } from 'class-transformer';
import { [2], ValidateNested } from 'class-validator';

export class ProfileDto {
  @ValidateNested()
  @[3](() => UserDto)
  user: UserDto;
}

Drag options to blanks, or click blank then click option'

AType

BIsString

CValidateNested

DIsNotEmpty

Attempts:

3 left

💡 Hint

Common Mistakes

Not importing Type causes nested validation to fail.

Confusing IsString with Type decorator.

The Type decorator from class-transformer is imported and used to specify the nested type. IsString is imported but not used here, showing common imports. ValidateNested is imported from class-validator but already used in code.