Schema definition in NestJS - Mini Project: Build & Apply

NestJS Schema Definition with Mongoose

📖 Scenario: You are building a simple NestJS application to manage a list of books in a library. Each book has a title, author, and number of pages.

🎯 Goal: Create a Mongoose schema in NestJS to define the structure of the Book documents stored in MongoDB.

📋 What You'll Learn

Create a Mongoose schema named BookSchema with fields title, author, and pages.

Set title and author as strings and pages as a number.

Add a configuration variable maxPages to limit the maximum number of pages.

Use the schema to create a model named Book.

💡 Why This Matters

🌍 Real World

Defining schemas is essential when working with databases in NestJS to ensure data is structured and validated correctly.

💼 Career

Understanding schema definition and validation is a key skill for backend developers working with NestJS and MongoDB.

1

Create the initial Book schema

Create a constant called BookSchema using new Schema from mongoose. Define fields title and author as strings, and pages as a number.

NestJS

import { Schema } from 'mongoose';

// Define BookSchema with title, author as strings and pages as number
// Your code here

Need a hint?

Use new Schema({ title: String, author: String, pages: Number }) to define the schema.

2

Add a maxPages configuration variable

Add a constant named maxPages and set it to 1000 to represent the maximum allowed pages for a book.

NestJS

import { Schema } from 'mongoose';

export const BookSchema = new Schema({
  title: String,
  author: String,
  pages: Number
});

// Add maxPages constant below
// Your code here

Need a hint?

Simply write export const maxPages = 1000; below the schema.

3

Add page limit validation to the schema

Update BookSchema to add a max validator on the pages field using the maxPages constant.

NestJS

import { Schema } from 'mongoose';

// Update pages field to include max validator
export const BookSchema = new Schema({
  title: String,
  author: String,
  pages: { type: Number, max: maxPages }
});

export const maxPages = 1000;

Need a hint?

Change pages: Number to pages: { type: Number, max: maxPages }.

4

Create and export the Book model

Import model from mongoose and create a constant Book by calling model with 'Book' and BookSchema. Export the Book constant.

NestJS

import { Schema, model } from 'mongoose';

export const maxPages = 1000;

export const BookSchema = new Schema({
  title: String,
  author: String,
  pages: { type: Number, max: maxPages }
});

// Create and export Book model below
// Your code here

Need a hint?

Use export const Book = model('Book', BookSchema); after importing model.