Mastering GraphQL Integration in a NestJS Project

As a web developer, you might already know NestJS is a progressive Node.js framework for building efficient, reliable, and scalable server-side applications. It uses TypeScript and combines elements of Object-Oriented Programming (OOP), Functional Programming (FP), and Reactive Programming (RP). On the other hand, GraphQL has become increasingly popular as a data query and manipulation language for APIs due to the vast flexibility and efficiency it provides in data fetching.

In this tutorial, we will walk you through the process of integrating GraphQL into your NestJS application. Additionally, we will shed light on some essential features and benefits of this powerful combination.

Setting up a NestJS projectlink

To begin, let's create a new NestJS project using the Nest CLI. If you haven't installed it yet, run:

npm install -g @nestjs/cli

Now, create a new project with:

nest new your-project-name

Navigate to your project directory and start your development server:

cd your-project-name
npm run start:dev

Your new NestJS project is now up and running.

Installing and Configuring GraphQLlink

To integrate GraphQL into your project, you must first install the following required dependencies:

npm install @nestjs/graphql graphql-tools graphql apollo-server-express

Now, let's import the GraphQLModule in your app.module.ts and configure it:

import { Module } from '@nestjs/common';
import { GraphQLModule } from '@nestjs/graphql';

@Module({
  imports: [
    GraphQLModule.forRoot({
      autoSchemaFile: 'schema.gql',
      context: ({ req }) => ({ req }),
    }),
  ],
})
export class AppModule {}

In the configuration above, we set autoSchemaFile to schema.gql. NestJS will automatically generate the GraphQL schema file based on the provided definitions.

Defining GraphQL Types and Resolverslink

To utilize GraphQL in your NestJS project, you need to define types and resolvers. Create a new directory photo inside the src folder and create two TypeScript files inside it: photo.entity.ts and photo.resolver.ts.

First, create a simple Photo entity as follows:

// src/photo/photo.entity.ts
import { ObjectType, Field, ID } from '@nestjs/graphql';

@ObjectType()
export class Photo {
  @Field(() => ID)
  id: number;

  @Field()
  url: string;

  @Field()
  description: string;
}

Now, let's create a sample resolver for the Photo entity:

// src/photo/photo.resolver.ts
import { Resolver, Query } from '@nestjs/graphql';
import { Photo } from './photo.entity';

@Resolver(() => Photo)
export class PhotoResolver {
  @Query(() => [Photo], { name: 'getAllPhotos' })
  async findAll(): Promise<Photo[]> {
    return [
      {
        id: 1,
        url: 'https://example.com/photo1.jpg',
        description: 'A beautiful sunset',
      },
      {
        id: 2,
        url: 'https://example.com/photo2.jpg',
        description: 'An amazing waterfall',
      },
    ];
  }
}

Import the AppModule into your app.module.ts file:

import { Module } from '@nestjs/common';
import { GraphQLModule } from '@nestjs/graphql';
import { PhotoResolver } from './photo/photo.resolver';

@Module({
  imports: [
    GraphQLModule.forRoot({
      autoSchemaFile: 'schema.gql',
      context: ({ req }) => ({ req }),
    }),
  ],
  providers: [PhotoResolver],
})
export class AppModule {}

Fetching Data with GraphQLlink

Your GraphQL server is now ready for use. You can access the GraphQL Playground by opening your browser and navigating to http://localhost:3000/graphql.

Test fetching data from your GraphQL server by executing the following query:

query {
  getAllPhotos {
    id
    url
    description
  }
}

You will receive the expected photos data.

Conclusionlink

In this tutorial, we successfully set up a NestJS application, integrated GraphQL, and showcased some of its essential features. Combining GraphQL with NestJS is a great way to enhance your app's functionality and optimize your data retrieval process. Give it a try and see the benefits for yourself.

For additional details about NestJS and GraphQL, don't hesitate to check their respective official documentation:

• NestJS Documentation
• GraphQL Documentation