Develop GraphQL API using NestJS with MongoDB

What is GraphQL?

GraphQL is an API query language developed by Facebook. It offers a more efficient, powerful, and flexible alternative to REST APIs. With GraphQL, clients can specify the exact data they need, and the server will respond with only that data. This reduces the amount of data transferred over the network, resulting in improved performance.

What is NestJS?

NestJS is a Node.js framework that allows developers to build efficient, scalable, and enterprise-grade server-side applications. It is built using TypeScript and combines OOP (Object Oriented Programming), FP (Functional Programming), and FRP (Functional Reactive Programming) concepts. Additionally, NestJS provides a powerful CLI tool that simplifies the process of creating new projects, modules, controllers, and services.

Pros and Cons of GraphQL

Pros

• More efficient data fetching: GraphQL allows clients to specify exactly what data they need, reducing the amount of data transferred over the network and improving performance.

• Strongly typed schema: GraphQL has a strongly typed schema that allows for better tooling and documentation.

• Flexibility: GraphQL allows clients to specify exactly what data they need, making it more flexible than REST APIs.

• Easy to evolve: GraphQL allows for easy evolution of the API without breaking changes.

Cons

• Complexity: GraphQL can be more complex than REST APIs, especially for simple use cases.

• Caching: GraphQL can be more difficult to cache than REST APIs, especially for complex queries.

• Learning curve: GraphQL has a steeper learning curve than REST APIs, especially for developers who are not familiar with the query language.

There are two major approaches to building GraphQL APIs:

1. Schema-first approach: In this approach, you describe the API in schema definition files or SDL, and NestJS generates Typescript definitions based on them.

2. Code-first approach: In this approach, you define queries, mutations, and other GraphQL functionalities using Typescript classes and decorators, and NestJS generates SDL files based on them.

In the following example, we are using the Code-first approach.

Prerequisites

Before we start, make sure you have the following installed on your system:

• Node.js (version 12 or higher)

• npm (version 6 or higher)

• MongoDB (version 4 or higher)

Implement GraphQL with NestJs and MongoDB

Step 1: Create a new NestJs project

To create a new NestJS project, open a terminal and run the following command:
npm i -g @nestjs/cli
nest new project-name

Step 2: Install the required dependencies

Next, we need to install the required dependencies for our project. Run the following command in the terminal:
npm i @nestjs/graphql graphql apollo-server-express mongoose
This will install the following packages:
• @nestjs/graphql: NestJS GraphQL module
• graphql-tools provides utilities for building GraphQL schemas.
• graphql: GraphQL library
• apollo-server-express: Apollo server for Express
• mongoose: MongoDB object modeling tool

Step 3: Create a new module

nest g module user

Step 4: Create a new resolver

nest g resolver user –no-spec

Step 5: Define the model

Step 6: Create a new service

nest g service user –no-spec

Step 7: Implement the service

Step 8: Inject the service into the resolver

Step 9: Configure the MongoDB connection

Step 10: Add the module to the app module

Step 11: Start the server

npm run start

Step 12: Test the API using a GraphQL client like GraphQL Playground

In conclusion, GraphQL is a powerful query language for APIs that offers a more efficient and flexible alternative to REST APIs. NestJS is a progressive Node.js framework that simplifies the process of building efficient, scalable server-side applications. By combining these two technologies, you can create APIs that are powerful, efficient, and flexible. However, it’s important to keep in mind that GraphQL has a steeper learning curve and can be more complex than REST APIs, especially for simple use cases.

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