Using GraphQL in NestJS

GraphQL offers a powerful query language that allows clients to request only the data they need, enabling more streamlined communication between clients and servers. GraphQL is a query language for your API that allows clients to request only the data they need, making it ideal for building efficient and flexible APIs.

Installing GraphQL Dependencies

To use GraphQL in your NestJS application, you'll need to install the following packages:

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

Configuring GraphQL in NestJS

Next, configure GraphQL in your NestJS application. Update the AppModule to enable the GraphQL module and define a GraphQL schema:

import { Module } from '@nestjs/common'; 
import { GraphQLModule } from '@nestjs/graphql'; 
import { CatsModule } from './cats/cats.module'; 

@Module({ 
 imports: [ 
      CatsModule, 
      GraphQLModule.forRoot({ autoSchemaFile: true, 
      }), 
   ],
}) 

export class AppModule {}        

In this example, autoSchemaFile: true tells NestJS to automatically generate a GraphQL schema based on your resolvers.

Creating GraphQL Resolvers

Create a resolver for your GraphQL queries and mutations. For example, in a cats.resolver.ts file:

import { Resolver, Query, Mutation, Args } from '@nestjs/graphql';
import { CatsService } from './cats.service';
import { Cat } from './cat.model';

@Resolver(() => Cat)
export class CatsResolver {
  constructor(private readonly catsService: CatsService) {}

  @Query(() => [Cat])
  async cats(): Promise<Cat[]> {
    return this.catsService.findAll();
  }

  @Mutation(() => Cat)
  async createCat(@Args('name') name: string): Promise<Cat> {
    return this.catsService.create(name);
  }
}        

Using GraphQL Playground

You can now use GraphQL Playground to interact with your GraphQL API. Start your NestJS application and navigate to https://localhost:3000/graphql in your web browser to access the playground.

GraphQL provides a flexible and efficient way to develop APIs, allowing clients to request only the data they need. In conclusion, GraphQL in NestJS offers a powerful approach to building APIs, providing flexibility and efficiency in data retrieval. By enabling clients to request only the data they need, GraphQL reduces over-fetching and under-fetching of data, improving overall API performance.