This short set of instructions gets you up and running with Apollo Angular. This guide is taken from the apollo-angular getting started guide from here

Installation

The simplest way to get started with Apollo Angular is by running ng add apollo-angular command.

Installation with Angular Schematics

We support ng-add command now.

To start using Apollo Angular simply run:

ng add apollo-angular

One thing you need to set is the URL of your GraphQL Server, so open src/app/graphql.module.ts and set uri variables:

const uri = 'https://api.apito.io/secured/graphql'; // our GraphQL API

Done! You can now create your first query, let's go through it together here

Installation without Angular Schematics

If you want to setup Apollo without the help of Angular Schematics, first, let's install some packages:

npm install apollo-angular @apollo/client graphql

• @apollo/client: Where the magic happens
• apollo-angular: Bridge between Angular and Apollo Client
• graphql: Second most important package

The @apollo/client package requires AsyncIterable so make sure your tsconfig.json includes es2020:

{
  "compilerOptions": {
    // ...
    "lib": [
      "es2020",
      "dom",
    ]
  }
}

Great, now that you have all the dependencies you need, let's create your first Apollo Client.

In our app.module.ts file use APOLLO_OPTIONS token to configure Apollo:

import {HttpClientModule} from '@angular/common/http';
import {ApolloModule, APOLLO_OPTIONS} from 'apollo-angular';
import {HttpLink} from 'apollo-angular/http';
import {InMemoryCache} from '@apollo/client/core';

@NgModule({
  imports: [BrowserModule, ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory: (httpLink: HttpLink) => {
        return {
            cache: new InMemoryCache(),
            link: httpLink.create({
                uri: 'https://api.apito.io/secured/graphql',
            }),
            headers: {
                Authorization: `Bearer API_SECRET`,
            },
        };
      },
      deps: [HttpLink],
    },
  ],
})
export class AppModule {}

Take a closer look what we did there:

1. With apollo-angular/http and HttpLink service we connect our client to an external GraphQL Server
2. Thanks to @apollo/client/core and InMemoryCache we have a place to store data in
3. APOLLO_OPTIONS provides options to Apollo Client

The HttpLink requires HttpClient so that's why we also used HttpClientModule from @angular/common/http.

Links and Cache

Apollo Angular has a pluggable network interface layer, which can let you configure how queries are sent over HTTP, or replace the whole network part with something completely custom, like a websocket transport, mocked server data, or anything else you can imagine.

One Link that you already have in your application is called HttpLink which uses HTTP to send your queries.

The InMemoryCache is the default cache implementation for Apollo Client 3.0.

Request data

Once all is hooked up, you're ready to start requesting data with Apollo service!

The Apollo is an Angular service exported from apollo-angular to share GraphQL data with your UI.

First, pass your GraphQL query wrapped in the gql or graphql function (from apollo-angular) to the query property in the Apollo.watchQuery method, in your component. The Apollo service is a regular angular service available to you, and your data is streamed through Observables.

The watchQuery method returns a QueryRef object which has the valueChanges property that is an Observable.

An object passed through an Observable contains loading, error, and data properties. Apollo Client tracks error and loading state for you, which will be reflected in the loading and error properties. Once the result of your query comes back, it will be attached to the data property.

It's also possible to fetch data only once. The query method of Apollo service returns an Observable that also resolves with the same result as above.

Let's create an ExchangeRates component to see the Apollo service in action!

Basic Operations

If you want to see how easy it is to fetch data from a GraphQL server with Apollo, you can use the query method. It is as easy as this:

import {Component, OnInit} from '@angular/core';
import {Apollo, gql} from 'apollo-angular';

@Component({
  selector: 'exchange-rates',
  template: `
    <div *ngIf="loading">
      Loading...
    </div>
    <div *ngIf="error">
      Error :(
    </div>
    <div *ngIf="rates">
      <div *ngFor="let rate of rates">
        <p>{{ rate.currency }}: {{ rate.rate }}</p>
      </div>
    </div>
  `,
})
export class ExchangeRates implements OnInit {
  rates: any[];
  loading = true;
  error: any;

  constructor(private apollo: Apollo) {}

  ngOnInit() {
    this.apollo
      .watchQuery({
        query: gql`
          {
            rates(currency: "USD") {
              currency
              rate
            }
          }
        `,
      })
      .valueChanges.subscribe((result: any) => {
        this.rates = result?.data?.rates;
        this.loading = result.loading;
        this.error = result.error;
      });
  }
}

Congrats, you just made your first query! 🎉 If you render your ExchangeRates component within your App component from the previous example, you'll first see a loading indicator and then data on the page once it's ready. Apollo Client automatically caches this data when it comes back from the server, so you won't see a loading indicator if you run the same query twice.

If you'd like to play around with the app we just built, you can view it on StackBlitz. Don't stop there! Try building more components with Apollo service and experimenting with the concepts you just learned.

Named clients

It is possible to have several apollo clients in the application, for example pointing to different endpoints.

In our app.module.ts file use ApolloModule and APOLLO_NAMED_OPTIONS token to configure Apollo Client:

import {HttpClientModule} from '@angular/common/http';
import {ApolloModule, APOLLO_NAMED_OPTIONS, NamedOptions} from 'apollo-angular';
import {HttpLink} from 'apollo-angular/http';
import {InMemoryCache} from '@apollo/client/core';

@NgModule({
  imports: [BrowserModule, ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_NAMED_OPTIONS, // <-- Different from standard initialization
      useFactory(httpLink: HttpLink): NamedOptions {
        return {
          newClientName: {
            // <-- this settings will be saved by name: newClientName
            cache: new InMemoryCache(),
            link: httpLink.create({
              uri: 'https://api.apito.io/secured/graphql',
            }),
            headers: {
                Authorization: `Bearer API_SECRET`,
            },
          },
        };
      },
      deps: [HttpLink],
    },
  ],
})
export class AppModule {}

Basic usage

import {Injectable} from '@angular/core';
import {Apollo, ApolloBase, gql} from 'apollo-angular';

@Injectable()
class ApiService {
  private apollo: ApolloBase;

  constructor(private apolloProvider: Apollo) {
    this.apollo = this.apolloProvider.use('newClientName');
  }

  getData(): Observable<ApolloQueryResult> {
    return this.apollo.watchQuery({
      query: gql`
        {
          rates(currency: "USD") {
            currency
            rate
          }
        }
      `,
    });
  }
}

Next steps

Now that you've learned how to fetch data with Apollo Angular, you're ready to dive deeper into creating more complex queries and mutations. After this section, we recommend moving onto:

• Queries: Learn how to fetch queries with arguments and dive deeper into configuration options..
• Mutations: Learn how to update data with mutations and when you'll need to update the Apollo cache.
• Apollo Client API: Sometimes, you'll need to access the client directly like we did in our plain JavaScript example above. Visit the API reference for a full list of options.