Built-in pipes (ParseIntPipe, ParseBoolPipe) in NestJS - Mini Project: Build & Apply

Using Built-in Pipes ParseIntPipe and ParseBoolPipe in NestJS

📖 Scenario: You are building a simple NestJS controller to handle user requests where some query parameters need to be converted to specific types automatically.For example, a user might send a query parameter age as a string, but you want it as a number. Similarly, a query parameter active might come as a string but should be treated as a boolean.

🎯 Goal: Create a NestJS controller with two GET routes that use the built-in pipes ParseIntPipe and ParseBoolPipe to automatically convert query parameters to the correct types.This will help ensure your controller methods receive the right data types without manual conversion.

📋 What You'll Learn

Create a controller class named UserController

Add a GET route /user/age that accepts a query parameter age and uses ParseIntPipe to convert it to a number

Add a GET route /user/active that accepts a query parameter active and uses ParseBoolPipe to convert it to a boolean

Use NestJS decorators @Controller, @Get, and @Query properly

Import ParseIntPipe and ParseBoolPipe from @nestjs/common

💡 Why This Matters

🌍 Real World

Web APIs often receive query parameters as strings. Using pipes like ParseIntPipe and ParseBoolPipe helps convert these strings to the correct types automatically, reducing manual parsing and errors.

💼 Career

Understanding and using NestJS built-in pipes is essential for backend developers working with NestJS to build robust and type-safe APIs.

1

Create the UserController class with imports

Create a NestJS controller class named UserController. Import Controller, Get, and Query from @nestjs/common. Do not add any methods yet.

NestJS

import { Controller, Get, Query } from '@nestjs/common';

// Create the UserController class with @Controller decorator
// Your code here

Need a hint?

Use @Controller('user') above the class declaration to set the route prefix.

2

Add ParseIntPipe import and age route method

Import ParseIntPipe from @nestjs/common. Add a GET route method named getAge with path 'age'. Use @Query('age', ParseIntPipe) to get the age query parameter as a number. The method should return the age value.

NestJS

import { Controller, Get, Query, ParseIntPipe } from '@nestjs/common';

@Controller('user')
export class UserController {
  // Add getAge method below
  // Your code here
}

Need a hint?

Use @Get('age') above the method and @Query('age', ParseIntPipe) to convert the query parameter.

3

Add ParseBoolPipe import and active route method

Import ParseBoolPipe from @nestjs/common. Add a GET route method named getActive with path 'active'. Use @Query('active', ParseBoolPipe) to get the active query parameter as a boolean. The method should return the active value.

NestJS

import { Controller, Get, Query, ParseIntPipe, ParseBoolPipe } from '@nestjs/common';

@Controller('user')
export class UserController {
  @Get('age')
  getAge(@Query('age', ParseIntPipe) age: number): number {
    return age;
  }

  // Add getActive method below
  // Your code here
}

Need a hint?

Use @Get('active') and @Query('active', ParseBoolPipe) to convert the query parameter to boolean.

4

Complete the UserController with both routes

Ensure the UserController class includes both getAge and getActive methods with their respective pipes and returns. The class should be decorated with @Controller('user') and import all necessary decorators and pipes from @nestjs/common.

NestJS

import { Controller, Get, Query, ParseIntPipe, ParseBoolPipe } from '@nestjs/common';

// Confirm the UserController class is complete with both methods
// Your code here

Need a hint?

Make sure both methods and imports are present and correctly used.