Multi-client

Overview

Apollo Orbit supports having multiple clients in the same Angular application. This is useful when you need to connect to multiple GraphQL APIs.

This is accomplished using provideApolloInstance function. It accepts two parameters, the first is the injection token to be used for the client, and the second is the client's options.

Setup

Let's assume for this example that the frontend needs to communicate with 2 GraphQL APIs:

1. A standard backend for frontend API
2. A billing API

Step 1: Create new client injection token

This token will be used to inject the billing client into the application.

app/graphql/apollo-billing.ts

import { Apollo } from '@apollo-orbit/angular';

export class ApolloBilling extends Apollo {
  public static readonly id = 'billing';
}

Step 2: Update app providers

import { ApolloBilling } from './apollo-billing';
import { provideApolloInstance, ... } from '@apollo-orbit/angular';

{
  providers: [
    provideApolloOrbit(
      withApolloOptions(() => ({
        cache: new InMemoryCache(),
        link: inject(HttpLinkFactory).create({ uri: 'http://api.backend.dev/graphql' })
      })),
      withHttpLink()
    ),
    provideApolloInstance(ApolloBilling, () => ({
      cache: new InMemoryCache(),
      id: ApolloBilling.id,
      link: inject(HttpLinkFactory).create({ uri: 'http://api.billing.dev/graphql' })
    }))
  ]
}

note

It is required to provide a unique id for each client. This id is used for associating the client with a state definition.

Step 3: Use the client

Now, the client can be injected just like any other Angular service.

import { ApolloBilling } from 'app/graphql/apollo-billing';

@Component({
  selector: 'app-billing',
  templateUrl: './billing.component.html',
  styleUrls: ['./billing.component.css']
})
export class BillingComponent {
  protected readonly invoicesQuery = this.apolloBilling.watchQuery(new InvoicesQuery());

  public constructor(
    private readonly apolloBilling: ApolloBilling
  ) { }
}

Step 4: Defining state for the client (Optional)

This is accomplished using clientId function available on the state descriptor.

app/billing/states/invoice.state.ts

import { ApolloBilling } from 'app/graphql/apollo-billing';

export const invoiceState = state(descriptor => descriptor
  .clientId(ApolloBilling.id)
  ...
);