Built-in pipes (ParseIntPipe, ParseBoolPipe) in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the ParseIntPipe in NestJS?

ParseIntPipe converts a string input from a request into an integer. It ensures the value is a valid number and throws an error if not.

beginner

How does ParseBoolPipe interpret string values?

ParseBoolPipe converts string inputs like 'true' or 'false' (case insensitive) into boolean true or false. It throws an error for invalid boolean strings.

beginner

Show a simple example of using ParseIntPipe in a controller route parameter.

In a controller method, use @Param('id', ParseIntPipe) id: number to automatically convert the 'id' parameter to a number.

intermediate

What happens if ParseIntPipe receives a non-numeric string?

It throws a BadRequestException, causing NestJS to respond with a 400 error indicating invalid input.

intermediate

Why use built-in pipes like ParseIntPipe and ParseBoolPipe instead of manual conversion?

They simplify code by automatically validating and converting inputs, improving reliability and reducing boilerplate error checks.

What does ParseIntPipe do in NestJS?

A Converts string input to an integer

B Converts boolean input to string

C Parses JSON objects

D Encrypts input data

ParseIntPipe converts string inputs to integers and validates them.

Which string value will ParseBoolPipe convert to false?

A "true"

B "false"

C "yes"

D "1"

ParseBoolPipe converts 'false' (case insensitive) to boolean false.

What error does ParseIntPipe throw on invalid input?

A InternalServerErrorException

B UnauthorizedException

C NotFoundException

D BadRequestException

ParseIntPipe throws BadRequestException for invalid integer input.

How do you apply ParseIntPipe to a route parameter named 'id'?

A @Param('id', ParseIntPipe) id: number

B @Body('id', ParseIntPipe) id: number

C @Query('id', ParseIntPipe) id: number

D @Headers('id', ParseIntPipe) id: number

Use @Param decorator with ParseIntPipe to convert route parameters.

Why prefer built-in pipes over manual parsing?

A They add extra features like caching

B They slow down the app for security

C They automatically validate and convert inputs

D They replace database queries

Built-in pipes simplify input validation and conversion, reducing errors.

Explain how ParseIntPipe works and when you would use it in a NestJS controller.

Think about converting URL parameters to numbers safely.

Describe the behavior of ParseBoolPipe and how it handles different string inputs.

Consider how to safely get true/false from user input.