DEV Community

Cover image for Explain how to create GraphQL API with Nest.js and provide step by step guide with explanation?
Nadim Chowdhury
Nadim Chowdhury

Posted on

Explain how to create GraphQL API with Nest.js and provide step by step guide with explanation?

Creating a GraphQL API with Nest.js involves several key steps, including setting up the Nest.js project, installing necessary packages, configuring GraphQL with Apollo Server, defining GraphQL schemas and resolvers, and integrating with a database if needed. Below is a detailed, step-by-step guide to building a GraphQL API using Nest.js:

Step 1: Initialize the Nest.js Project

First, you need to create a new Nest.js project. If you haven't installed the Nest CLI, you can do so and then create the project:

npm i -g @nestjs/cli
nest new graphql-project
cd graphql-project
Enter fullscreen mode Exit fullscreen mode

This command sets up a new Nest.js project with all necessary dependencies.

Step 2: Install GraphQL and Apollo Server Packages

Nest.js uses Apollo Server for serving GraphQL APIs. Install the necessary GraphQL packages:

npm install @nestjs/graphql @nestjs/apollo graphql apollo-server-express
Enter fullscreen mode Exit fullscreen mode

Step 3: Setup GraphQL Module

You will need to configure the GraphQL module within your Nest.js project. Modify the app.module.ts to include the GraphQLModule:

import { Module } from '@nestjs/common';
import { GraphQLModule } from '@nestjs/graphql';
import { ApolloDriver, ApolloDriverConfig } from '@nestjs/apollo';

  imports: [
      driver: ApolloDriver,
      autoSchemaFile: true,  // Generates schema file automatically in memory
export class AppModule {}
Enter fullscreen mode Exit fullscreen mode

In this configuration:

  • autoSchemaFile: true tells Apollo to generate the schema file automatically and keep it in memory. You can also specify a path to generate the file on disk.

Step 4: Define GraphQL Types and Resolvers

Create Entities

Entities are classes that you can use both as TypeORM entities and GraphQL types. Create an entity:

import { ObjectType, Field, ID } from '@nestjs/graphql';

export class Recipe {
  @Field(() => ID)
  id: string;

  title: string;

  @Field({ nullable: true })
  description?: string;
Enter fullscreen mode Exit fullscreen mode

Create Resolvers

Resolvers handle the GraphQL queries and mutations. Create a resolver:

nest generate resolver recipes
Enter fullscreen mode Exit fullscreen mode

Now, implement it:

import { Resolver, Query, Args, Mutation } from '@nestjs/graphql';
import { Recipe } from './recipe.entity';

@Resolver(of => Recipe)
export class RecipesResolver {
  private recipes: Recipe[] = [];

  @Query(returns => Recipe)
  async getRecipe(@Args('id', { type: () => String }) id: string): Promise<Recipe> {
    return => === id);

  @Query(returns => [Recipe])
  async getRecipes(): Promise<Recipe[]> {

  @Mutation(returns => Recipe)
  async addRecipe(
    @Args('title') title: string,
    @Args('description', { nullable: true }) description: string,
  ): Promise<Recipe> {
    const recipe = { id:, title, description };;
    return recipe;
Enter fullscreen mode Exit fullscreen mode

Step 5: Integrate with a Database (Optional)

If you want to integrate a database like PostgreSQL using TypeORM, install additional packages and configure the TypeOrmModule in your app.module.ts. This process has been detailed in previous answers.

Step 6: Run Your Nest.js Application

Run your application to see your GraphQL API in action:

npm run start
Enter fullscreen mode Exit fullscreen mode

Step 7: Test Your GraphQL API

Visit http://localhost:3000/graphql in your browser to access the Apollo Studio, where you can test your GraphQL queries and mutations.

Final Thoughts

This setup provides a basic overview of creating a GraphQL API in Nest.js. For a real-world application, you'd need to consider additional aspects such as authentication, more complex business logic, testing, and proper error handling. This guide gives you a foundation, and you can build upon it based on your application's requirements.

Disclaimer: This content is generated by AI.

Top comments (0)