How to make a complete/proper GraphQL API with Nest.js?
Published: 2024-05-17 13:25:52

Creating a complete and proper GraphQL API with Nest.js involves several key steps, from setting up your Nest.js environment to defining schemas, resolvers, and integrating with a database. Here's a detailed guide to help you build a GraphQL API using Nest.js:

### 1. Setting Up Your Nest.js Project

First, you need to create a new Nest.js project if you haven't already. You can do this by installing the Nest CLI and creating a new project:

```bash
npm i -g @nestjs/cli
nest new project-name
cd project-name
```

### 2. Install GraphQL and Apollo Server Packages

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

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

### 3. Set Up GraphQL Module

Create a GraphQL module using the Nest CLI and configure it in your app:

```bash
nest generate module graphql
```

In your `app.module.ts`, import the `GraphQLModule` and configure it:

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

@Module({
  imports: [
    GraphQLModule.forRoot<ApolloDriverConfig>({
      driver: ApolloDriver,
      autoSchemaFile: 'schema.gql',  // Generates schema automatically in memory
    }),
  ],
})
export class AppModule {}
```

### 4. Define Your GraphQL Schemas

You can define your schemas using either code first or schema first approach. Here’s an example using the code first approach:

Create a `recipe.entity.ts`:

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

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

  @Field()
  title: string;

  @Field({ nullable: true })
  description?: string;
}
```

### 5. Create Resolvers

Resolvers are where you define the methods that will respond to the GraphQL queries. Create a resolver for the `Recipe`:

```bash
nest generate resolver recipe
```

Implement the resolver in `recipe.resolver.ts`:

```typescript
import { Query, Resolver } from '@nestjs/graphql';
import { Recipe } from './entities/recipe.entity';

@Resolver(of => Recipe)
export class RecipeResolver {
  @Query(returns => [Recipe])
  async recipes(): Promise<Recipe[]> {
    return [
      {
        id: '1',
        title: 'First Recipe',
        description: 'Delicious first recipe',
      },
    ];
  }
}
```

### 6. Integrate with a Database

To make your API dynamic, integrate it with a database like MongoDB or PostgreSQL. For example, using TypeORM with PostgreSQL:

```bash
npm install @nestjs/typeorm typeorm pg
```

Configure the TypeORM module in your `app.module.ts` and use repositories in your services to interact with the database.

### 7. Authentication and Authorization

For securing your GraphQL API, you might want to add authentication and authorization:

- **Authentication**: You can use Passport with JWT or other strategies to authenticate users.
- **Authorization**: You can use Guards to protect specific routes or use field-level authorization with directives.

### 8. Testing and Documentation

- **Testing**: Write unit and e2e tests using Jest that comes pre-configured with Nest.js.
- **Documentation**: Although GraphQL has built-in documentation through the playground, you may want to maintain a versioned API documentation using tools like Swagger (for REST) or GraphDoc (for GraphQL).

By following these steps, you'll have a robust, scalable, and secure GraphQL API using Nest.js.

Disclaimer: This content is generated by AI.