Injectable decorator in NestJS - Mini Project: Build & Apply

Using the Injectable Decorator in NestJS

📖 Scenario: You are building a simple NestJS service to manage a list of books in a library. You want to make this service available for other parts of your application by marking it as injectable.

🎯 Goal: Create a NestJS service class called BooksService and use the @Injectable() decorator to make it injectable in other parts of the app.

📋 What You'll Learn

Create a class named BooksService

Use the @Injectable() decorator from @nestjs/common

Define a property books as an array of strings with these exact values: '1984', 'Brave New World', 'Fahrenheit 451'

Add a method getBooks() that returns the books array

💡 Why This Matters

🌍 Real World

Services in NestJS are used to hold business logic and data. Marking them with @Injectable() allows NestJS to manage their lifecycle and inject them where needed.

💼 Career

Understanding how to create injectable services is essential for building scalable and maintainable backend applications with NestJS, a popular Node.js framework.

1

Create the BooksService class with a books array

Create a class called BooksService with a property books that is an array containing the strings '1984', 'Brave New World', and 'Fahrenheit 451'.

NestJS

# Your code here

Need a hint?

Start by writing export class BooksService {} and inside it add books = ['1984', 'Brave New World', 'Fahrenheit 451'];

2

Import the Injectable decorator

Add an import statement to import Injectable from @nestjs/common at the top of the file.

NestJS

// Add import for Injectable from '@nestjs/common'

export class BooksService {
  books = ['1984', 'Brave New World', 'Fahrenheit 451'];
}

Need a hint?

Write import { Injectable } from '@nestjs/common'; at the top of your file.

3

Add the @Injectable() decorator to BooksService

Add the @Injectable() decorator exactly above the BooksService class declaration.

NestJS

import { Injectable } from '@nestjs/common';

// Add @Injectable() decorator here
export class BooksService {
  books = ['1984', 'Brave New World', 'Fahrenheit 451'];
}

Need a hint?

Place @Injectable() right before export class BooksService.

4

Add a getBooks() method to return the books array

Inside the BooksService class, add a method called getBooks() that returns the books array.

NestJS

import { Injectable } from '@nestjs/common';

@Injectable()
export class BooksService {
  books = ['1984', 'Brave New World', 'Fahrenheit 451'];

  // Add getBooks() method here
}

Need a hint?

Write a method getBooks() that returns this.books.