Network Layer

Apollo Angular comes with two kinds of network layer based on Angular’s HttpClient.

Http Link

An Apollo Link to allow sending a single http request per operation. It’s based on Angular’s HttpClient.

Why not @apollo/client/link/http? You get SSR for free, ability to use Http Interceptors and easier testing.

Usage

import { APOLLO_OPTIONS, ApolloModule } from 'apollo-angular';
import { HttpLink } from 'apollo-angular/http';
 
@NgModule({
  imports: [ApolloModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpLink) {
        return {
          // other options
          link: httpLink.create({ uri: '/graphql' }),
        };
      },
      deps: [HttpLink],
    },
  ],
})
class AppModule {}

HttpClient

The HTTP Link relies on having HttpClient (from @angular/common/http) present in your application.

Options

HTTP Link takes an object with some options on it to customize the behavior of the link. If your server supports it, the HTTP link can also send over metadata about the request in the extensions field. To enable this, pass includeExtensions as true. If you would like to use persisted queries or just not to send a query, disable includeQuery.

name	value	default	required
uri	string / function	`/graphql`	false
includeExtensions	boolean	`false`	false
includeQuery	boolean	`true`	false
headers	HttpHeaders	`none`	false
withCredentials	boolean	`none`	false
method	string	`POST`	false
useGETForQueries	boolean	`false`	false

Context

The HTTP Link uses the headers field on the context to allow passing headers to the HTTP request. It also supports the withCredentials field for defining credentials policy for request. These options will override the same key if passed when creating the the link. If some setting is different than the one in Options, this one will be used.

name	value	default	required
uri	string	`as in options`	false
includeExtensions	boolean	`as in options`	false
includeQuery	boolean	`as in options`	false
headers	HttpHeaders	none	false
withCredentials	boolean	`as in options`	false
method	string	`as in options`	false
useMultipart	boolean	`as in options`	false

import { Apollo, APOLLO_OPTIONS } from 'apollo-angular';
import { HttpLink } from 'apollo-link/http';
import { HttpClientModule } from '@angular/common/http';
import { InMemoryCache } from '@apollo/client/core';
 
@NgModules({
  imports: [ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpLink) {
        return {
          link: httpLink.create({ uri: '/graphql' }),
          cache: new InMemoryCache(),
        };
      },
      deps: [HttpLink],
    },
  ],
})
class AppModule {}
 
// a query with apollo-angular
// somewhere in Component
apollo.query({
  query: MY_QUERY,
  context: {
    // example of setting the headers with context per operation
    headers: new HttpHeaders().set('X-Custom-Header', 'custom-value'),
  },
});

Uri as function

@NgModules({
  imports: [ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpLink) {
        return {
          link: httpLink.create({
            uri(operation) {
              return operation.operationName === 'login' ? '/auth' : '/graphq';
            },
          }),
          cache: new InMemoryCache(),
        };
      },
      deps: [HttpLink],
    },
  ],
})
class AppModule {}

File Upload

In order to upload a file, you need to turn on useMultipart flag:

apollo.query({
  query: MY_QUERY,
  context: {
    useMultipart: true,
  },
});

Middleware

import { HttpLink } from 'apollo-angular/http';
import { ApolloLink } from '@apollo/client/core';
 
@NgModules({
  imports: [ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpLink) {
        const http = httpLink.create({ uri: '/graphql' });
        const middleware = new ApolloLink((operation, forward) => {
          operation.setContext({
            headers: new HttpHeaders().set(
              'Authorization',
              `Bearer ${localStorage.getItem('token') || null}`,
            ),
          });
          return forward(operation);
        });
 
        const link = middleware.concat(http);
 
        return {
          link,
          cache: new InMemoryCache(),
        };
      },
      deps: [HttpLink],
    },
  ],
})
class AppModule {}

Afterware (error)

import { HttpLink } from 'apollo-angular/http';
import { ApolloLink } from '@apollo/client/core';
import { onError } from '@apollo/client/link/error';
import { Auth } from './auth.service';
 
@NgModules({
  imports: [ApolloModule, HttpClientModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpLink) {
        const http = httpLink.create({ uri: '/graphql' });
        const error = onError(({ networkError }) => {
          if (networkError.status === 401) {
            auth.logout();
          }
        });
 
        const link = error.concat(http);
 
        return {
          link,
          cache: new InMemoryCache(),
        };
      },
      deps: [HttpLink],
    },
  ],
})
class AppModule {}

Http Batching Link

An Apollo Link to combine multiple GraphQL operations into single HTTP request.

Usage

import { HttpBatchLink } from 'apollo-angular/http';
 
@NgModule({
  imports: [ApolloModule],
  providers: [
    {
      provide: APOLLO_OPTIONS,
      useFactory(httpLink: HttpBatchLink) {
        return {
          // other options
          link: httpLink.create({ uri: '/graphql' }),
        };
      },
      deps: [HttpBatchLink],
    },
  ],
})
class AppModule {}

HttpClient

The HTTP Link relies on having HttpClient (from @angular/common/http) present in your application.

Options

Accepts the same options as HttpLink.

BatchOptions

The batching options indicate how operations are batched together.

name	value	default	required
batchInterval	number	10	false
batchMax	number	10	false
batchKey	Function	-	false

batchInterval - the maximum time a batch will wait before automatically being sent over the network
batchMax - the size of batches
batchKey a function that accepts an operation and returns a string key, which uniquely names the batch the operation belongs to, defaults to returning the same string.

💡

Note: batchKey by default batches together requests with the same uri and the same options. Since options from an operation’s context overwrites those from a link you could end up with few differents keys and what it means, few separate requests.

Context

Works in the same way as in HttpLink.

To skip batching you can set skipBatching: true in operation’s context.

💡

Note: skipBatching works only with the default batchKey. To create custom one you should check if skipBatching is set in context and generate a random batchKey for that operation.

Query, Mutation, Subscription Services Pagination