DTO class creation in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does DTO stand for in NestJS?

DTO stands for Data Transfer Object. It is a simple object used to carry data between processes or layers in an application.

beginner

Why do we use DTO classes in NestJS?

We use DTO classes to define how data should be sent or received. They help validate and type-check data, making the app safer and easier to maintain.

beginner

How do you create a simple DTO class in NestJS?

You create a class with properties that match the data you expect. For example:<br><pre>export class CreateUserDto {
  name: string;
  age: number;
}</pre>

intermediate

What decorator is commonly used with DTO properties for validation in NestJS?

Decorators from the class-validator package like @IsString(), @IsInt(), and @IsNotEmpty() are used to validate DTO properties.

intermediate

How does NestJS use DTO classes in controllers?

NestJS uses DTO classes to type-check and validate incoming request data automatically when you use them as method parameters with decorators like @Body().

What is the main purpose of a DTO class in NestJS?

A To define the shape of data sent or received

B To handle database queries

C To create UI components

D To manage server configuration

DTO classes define how data should look when sent or received, helping with validation and type safety.

Which package provides decorators like @IsString() for DTO validation?

A class-transformer

B nestjs/common

C rxjs

D class-validator

The class-validator package provides decorators to validate DTO properties.

How do you apply a DTO class to validate incoming data in a NestJS controller?

A Use @Body() decorator with the DTO class as type

B Use @Param() decorator

C Use @Injectable() decorator

D Use @Get() decorator

You use the @Body() decorator and specify the DTO class type to validate incoming request body data.

Which of these is a valid DTO property declaration in NestJS?

A function name() {}

B name: string;

C const name = 'string';

D let name: string = '';

DTO properties are declared as class properties with types, like 'name: string;'.

What happens if incoming data does not match the DTO validation rules?

A The request is accepted without changes

B The server restarts

C NestJS throws a validation error and rejects the request

D The data is automatically corrected

NestJS rejects requests with invalid data by throwing validation errors when DTO validation fails.

Explain what a DTO class is and why it is useful in NestJS applications.

Think about how data moves between client and server and how to keep it safe and clear.

Describe the steps to create and use a DTO class for validating user input in a NestJS controller.

Focus on class creation, decorators, and controller usage.