Route parameters in NestJS - Mini Project: Build & Apply

Handling Route Parameters in NestJS

📖 Scenario: You are building a simple NestJS API for a bookstore. You want to create a route that can receive a book's ID as a parameter in the URL and return details about that book.

🎯 Goal: Build a NestJS controller with a route that accepts a bookId as a route parameter and returns a message including that bookId.

📋 What You'll Learn

Create a controller named BooksController.

Add a route handler method named getBookById.

Use the @Param decorator to extract the bookId from the route.

Return a string message that includes the bookId.

💡 Why This Matters

🌍 Real World

Route parameters are used in web APIs to identify specific resources, like books, users, or orders, by their unique IDs in the URL.

💼 Career

Understanding route parameters is essential for backend developers building RESTful APIs with frameworks like NestJS.

1

Create the BooksController class

Create a class called BooksController and decorate it with @Controller('books').

NestJS

@Controller('books')
export class BooksController {
  // Your code here
}

Need a hint?

Use @Controller('books') above the class to define the route prefix.

2

Add the getBookById method with route parameter

Inside BooksController, add a method called getBookById decorated with @Get(':bookId') to handle GET requests with a bookId parameter.

NestJS

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

@Controller('books')
export class BooksController {
  // Your code here
}

Need a hint?

Use @Get(':bookId') to define the route with a parameter named bookId.

3

Extract the bookId parameter using @Param decorator

Modify the getBookById method to accept a parameter called bookId using the @Param('bookId') decorator from @nestjs/common.

NestJS

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

@Controller('books')
export class BooksController {
  @Get(':bookId')
  getBookById(@Param('bookId') bookId: string) {
    // Your code here
  }
}

Need a hint?

Import @Param and use it to get the bookId from the URL.

4

Return a message including the bookId

Inside the getBookById method, return a string like `Book ID requested is: ${bookId}` that includes the bookId parameter.

NestJS

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

@Controller('books')
export class BooksController {
  @Get(':bookId')
  getBookById(@Param('bookId') bookId: string) {
    // Your code here
  }
}

Need a hint?

Use a template string to include the bookId in the returned message.