Schema-first approach in NestJS - Mini Project: Build & Apply

Building a GraphQL API with NestJS Using Schema-First Approach

📖 Scenario: You are creating a simple GraphQL API for a bookstore. You want to define your data types and queries using GraphQL schema language first, then implement the resolvers in NestJS.

🎯 Goal: Build a NestJS GraphQL API using the schema-first approach. Define a GraphQL schema for books, configure the GraphQL module, implement resolvers to return book data, and complete the setup to serve the API.

📋 What You'll Learn

Create a GraphQL schema file with a Book type and a Query to get all books

Configure the NestJS GraphQL module to use the schema file

Implement a resolver class with a method to return a list of books

Complete the module setup to include the resolver and GraphQL configuration

💡 Why This Matters

🌍 Real World

Many modern backend APIs use GraphQL to allow clients to request exactly the data they need. The schema-first approach helps teams design the API contract before coding.

💼 Career

Understanding schema-first GraphQL with NestJS is valuable for backend developers working on scalable APIs and microservices.

1

Create GraphQL Schema File

Create a file named books.schema.graphql with a Book type that has id (ID!), title (String!), and author (String!) fields. Also add a Query type with a field books that returns a list of Book.

NestJS

# Create books.schema.graphql with Book type and Query type
# Your code here

Need a hint?

Use GraphQL SDL syntax. Define Book type first, then Query with books field returning a list of Book.

2

Configure GraphQL Module in NestJS

In app.module.ts, import GraphQLModule from @nestjs/graphql and configure it with typePaths pointing to ./**/*.schema.graphql. Use autoSchemaFile: false to disable auto schema generation.

NestJS

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

@Module({
  imports: [
    // Configure GraphQLModule here
  ],
})
export class AppModule {}

# Your code here

Need a hint?

Use GraphQLModule.forRoot with typePaths array and set autoSchemaFile to false.

3

Implement Books Resolver

Create a resolver class named BooksResolver with a method books() decorated with @Query('books'). Return an array of book objects with id, title, and author matching the schema.

NestJS

import { Resolver, Query } from '@nestjs/graphql';

@Resolver('Book')
export class BooksResolver {
  // Add books query method here
  // Your code here
}

Need a hint?

Use @Resolver('Book') on the class and @Query('books') on the method. Return an array of objects matching the Book type.

4

Complete Module Setup with Resolver

In app.module.ts, import BooksResolver and add it to the providers array in the @Module decorator to complete the GraphQL API setup.

NestJS

import { Module } from '@nestjs/common';
import { GraphQLModule } from '@nestjs/graphql';
import { BooksResolver } from './books.resolver';

@Module({
  imports: [
    GraphQLModule.forRoot({
      typePaths: ['./**/*.schema.graphql'],
      autoSchemaFile: false,
    }),
  ],
  providers: [
    // Add BooksResolver here
  ],
})
export class AppModule {}

# Your code here

Need a hint?

Import BooksResolver and add it to the providers array inside the @Module decorator.