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Guide: Angular

GraphQL Code Generator provides the @graphql-codegen/typescript-apollo-angular plugin that generates full-typed Apollo GraphQL services.

Taking the following schema:

schema.graphql
type Author {
  id: Int!
  firstName: String!
  lastName: String!
  posts(findTitle: String): [Post]
}
 
type Post {
  id: Int!
  title: String!
  author: Author
}
 
type Query {
  posts: [Post]
}

Most Apollo Client usage in Angular will look as follows:

const GET_POSTS = gql`
  query Posts {
    posts {
      id
      title
      author {
        id
        firstName
        lastName
      }
    }
  }
`
 
interface Post {
  id: string
  title: string
  author?: {
    id: string
    firstName: string
    lastName: string
  }
}
 
@Component({
  /* … */
})
class PostsComponent implements OnInit, OnDestroy {
  posts: Post[]
 
  private querySubscription: Subscription
 
  ngOnInit() {
    this.querySubscription = this.apollo
      .watchQuery({
        query: GET_POSTS
      })
      .valueChanges.subscribe(({ data }) => {
        this.posts = data.posts as Post[]
      })
  }
  ngOnDestroy() {
    this.querySubscription.unsubscribe()
  }
}

Not typing or manually maintaining the data-types can lead to many issues:

  • outdated typing (regarding the current Schema)

  • typos

  • partial typing of data (not all Schema’s fields has a corresponding type)

For this reason, GraphQL Code Generator provides a @graphql-codegen/typescript-apollo-angular plugin that generates typed Apollo services for each GraphQL operation.

Just a few configuration steps are required to get those Apollo services:

Install

npm i graphql
npm i -D typescript
npm i -D @graphql-codegen/cli
npm i -D @graphql-codegen/typescript
npm i -D @graphql-codegen/typescript-operations
npm i -D @graphql-codegen/typescript-apollo-angular

Configure the plugin

Create or update your codegen.ts file as follows:

codegen.ts
import type { CodegenConfig } from '@graphql-codegen/cli'
 
const config: CodegenConfig = {
  schema: 'http://my-graphql-api.com/graphql',
  documents: './src/**/*.ts',
  generates: {
    './graphql/generated.ts': {
      plugins: ['typescript', 'typescript-operations', 'typescript-apollo-angular']
    }
  }
}
export default config
💡

schema and documents values

schema needs to be your target GraphQL API URL ("/graphql" included).

documents is a glob expression to your .graphql or .ts files.

Run the codegen and update your code

Assuming that, as recommended, your package.json has the following script:

package.json
{
  "scripts": {
    "generate": "graphql-codegen"
  }
}

Running the following generates the graphql/generated.ts file.

npm run generate

We can now update our code as follows:

import { PostsGQL, PostsQuery } from './graphql'
// BE SURE TO USE Observable from `rxjs` and not from `@apollo/client/core` when using map
import { Observable } from 'rxjs'
import { map } from 'rxjs/operators'
 
@Component({
  /* … */
})
export class PostsComponent {
  posts: Observable<PostsQuery['posts']>
 
  constructor(postsGQL: PostsGQL) {
    this.posts = postsGQL.watch().valueChanges.pipe(map(result => result.data.posts))
  }
}

For more advanced configuration, please refer to the plugin documentation.

For a different organization of the generated files, please refer to the “Generated files colocation” page.

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