Apollo Client subscriptions for GraphQL

This is the seventh instalment of our full-stack GraphQL + React tutorial, which walks you through building a messaging app. Each section is self-contained and focuses on a few new subjects, so you may start where you choose or go through the entire series…

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GraphQL Subscriptions in Apollo Client

GraphQL subscriptions are based on a simple publish-subscribe system. In our server-side subscriptions package, when a client makes a subscription, we simply use a map from one subscription name to one or more channel names to subscribe to the right channels. The subscription query will be re-run every time something is published to one of these channels. We think a common pattern will be to publish mutation results to a channel, so a subscription can send a new result to clients whenever a mutation happens. This is why some people call subscriptions the result of someone else’s mutation .

#apollo client #subscriptions #graphql

How We Built GraphQL Subscriptions with Apollo

A real-world example
At Scaphold, we manage a lot of infrastructure to make sure our customers’ APIs stay available and performant. One of our core features is a graphical schema designer that allows you to easily define the GraphQL schema that will come to define your Scaphold API. What you don’t see when playing around with our schema designer, however, is a complex migration system that makes sure your API’s database is always up to date and in adherence with your schema. When you make a migration to your schema, the machine that fields the migration request will make the necessary changes to your database so that your API stays in sync.

#graphql #graphql subscriptions #apollo

Apollo Client Data Normalization and Storage

Apollo client is a powerful frontend GraphQL library that allows an application using GraphQL to query itself, and the connected GraphQL data service. It is a client side state management library that integrates deeply with GraphQL backends.

Under the covers, Apollo client takes your GraphQL query response, and flattens it into a key-value storage system. Take the following example:

// GraphQL Query and Type
type Account { 
  id: ID!
  userName: String!
}
query getAccount() {
  account {
    id
    userName
    __typename // not required, but for illustration
  }  
}

The query above for a value on type Account, would return a response like this:

{
  data: {
    account: {
      id: 1,
      userName: 'user',
      __typename: 'Account'
    }
  }
}

#apollo #graphql #apollo-client #javascript #react

Apollo Client vs. Redux: Learnings and Experience

The ever changing world of front end development continues to evolve and introduce many different libraries to solve your problems. As GraphQL continues to grow in popularity, the tools and libraries surrounding it change also. Recently I helped write a new application that interacted solely with a GraphQL backend, and used Apollo Client (AC) to interact with instead of Redux in our React frontend application. Having previously written many javascript apps with Redux, here are some takeaways from my experience.

Disclaimer: Comparing the two libraries assumes you are working with a GraphQL backend. Apollo Client doesn’t work with other types of backends and isn’t a viable alternative to Redux in that case.

#graphql #redux #apollo-client #javascript #apollo

apollo-upload-client: A Terminating Apollo Link for Apollo Client that Fetches a GraphQL Multipart Request

Apollo Upload Client

A terminating Apollo Link for Apollo Client that fetches a GraphQL multipart request if the GraphQL variables contain files (by default FileList, File, Blob, or ReactNativeFile instances), or else fetches a regular GraphQL POST or GET request (depending on the config and GraphQL operation).

Installation

To install with npm, run:

npm install apollo-upload-client

Remove any uri, credentials, or headers options from the ApolloClient constructor.

Apollo Client can only have 1 terminating Apollo Link that sends the GraphQL requests; if one such as HttpLink is already setup, remove it.

Initialize the client with a terminating Apollo Link using createUploadLink.

Also ensure the GraphQL server implements the GraphQL multipart request spec and that uploads are handled correctly in resolvers.

Usage

Use FileList, File, Blob or ReactNativeFile instances anywhere within query or mutation variables to send a GraphQL multipart request.

See also the example API and client.

FileList

import { gql, useMutation } from "@apollo/client";

const MUTATION = gql`
  mutation ($files: [Upload!]!) {
    uploadFiles(files: $files) {
      success
    }
  }
`;

function UploadFiles() {
  const [mutate] = useMutation(MUTATION);

  function onChange({ target: { validity, files } }) {
    if (validity.valid) mutate({ variables: { files } });
  }

  return <input type="file" multiple required onChange={onChange} />;
}

File

import { gql, useMutation } from "@apollo/client";

const MUTATION = gql`
  mutation ($file: Upload!) {
    uploadFile(file: $file) {
      success
    }
  }
`;

function UploadFile() {
  const [mutate] = useMutation(MUTATION);

  function onChange({
    target: {
      validity,
      files: [file],
    },
  }) {
    if (validity.valid) mutate({ variables: { file } });
  }

  return <input type="file" required onChange={onChange} />;
}

Blob

import { gql, useMutation } from "@apollo/client";

const MUTATION = gql`
  mutation ($file: Upload!) {
    uploadFile(file: $file) {
      success
    }
  }
`;

function UploadFile() {
  const [mutate] = useMutation(MUTATION);

  function onChange({ target: { validity, value } }) {
    if (validity.valid) {
      const file = new Blob([value], { type: "text/plain" });

      // Optional, defaults to `blob`.
      file.name = "text.txt";

      mutate({ variables: { file } });
    }
  }

  return <input type="text" required onChange={onChange} />;
}

Requirements

• Node.js: ^12.22.0 || ^14.17.0 || >= 16.0.0
• Browsers: > 0.5%, not OperaMini all, not IE > 0, not dead
• React Native

Consider polyfilling:

• Promise
• fetch
• FormData

API

• class ReactNativeFile
• function createUploadLink
• function formDataAppendFile
• function isExtractableFile
• type ExtractableFileMatcher
• type FetchOptions
• type FormDataFileAppender
• type ReactNativeFileSubstitute

class ReactNativeFile

Used to mark React Native File substitutes as it’s too risky to assume all objects with uri, type and name properties are extractable files.

Parameter	Type	Description
file	ReactNativeFileSubstitute	A React Native File substitute.

See

• extract-files ReactNativeFile docs.

Examples

Ways to import.

import { ReactNativeFile } from "apollo-upload-client";

import ReactNativeFile from "apollo-upload-client/public/ReactNativeFile.js";

Ways to require.

const { ReactNativeFile } = require("apollo-upload-client");

const ReactNativeFile = require("apollo-upload-client/public/ReactNativeFile.js");

A file in React Native that can be used in query or mutation variables.

const file = new ReactNativeFile({  uri: uriFromCameraRoll,  name: "a.jpg",  type: "image/jpeg", });

---

function createUploadLink

Creates a terminating Apollo Link for Apollo Client that fetches a GraphQL multipart request if the GraphQL variables contain files (by default FileList, File, Blob, or ReactNativeFile instances), or else fetches a regular GraphQL POST or GET request (depending on the config and GraphQL operation).

Some of the options are similar to the createHttpLink options.

Parameter	Type	Description
options	object	Options.
options.uri	string? = /graphql	GraphQL endpoint URI.
options.useGETForQueries	boolean?	Should GET be used to fetch queries, if there are no files to upload.
options.isExtractableFile	ExtractableFileMatcher? = isExtractableFile	Customizes how files are matched in the GraphQL operation for extraction.
options.FormData	class?	FormData implementation to use, defaulting to the FormData global.
options.formDataAppendFile	FormDataFileAppender? = formDataAppendFile	Customizes how extracted files are appended to the FormData instance.
options.fetch	Function?	fetch implementation to use, defaulting to the fetch global.
options.fetchOptions	FetchOptions?	fetch options; overridden by upload requirements.
options.credentials	string?	Overrides options.fetchOptions.credentials.
options.headers	object?	Merges with and overrides options.fetchOptions.headers.
options.includeExtensions	boolean? = false	Toggles sending extensions fields to the GraphQL server.

Returns: ApolloLink — A terminating Apollo Link.

See

• GraphQL multipart request spec.

Examples

Ways to import.

import { createUploadLink } from "apollo-upload-client";

import createUploadLink from "apollo-upload-client/public/createUploadLink.js";

Ways to require.

const { createUploadLink } = require("apollo-upload-client");

const createUploadLink = require("apollo-upload-client/public/createUploadLink.js");

A basic Apollo Client setup.

import { ApolloClient, InMemoryCache } from "@apollo/client"; import createUploadLink from "apollo-upload-client/public/createUploadLink.js"; const client = new ApolloClient({  cache: new InMemoryCache(),  link: createUploadLink(), });

---

function formDataAppendFile

The default implementation for createUploadLink options.formDataAppendFile that uses the standard FormData.append method.

Type: FormDataFileAppender

Parameter	Type	Description
formData	FormData	FormData instance to append the specified file to.
fieldName	string	Field name for the file.
file	*	File to append.

Examples

Ways to import.

import { formDataAppendFile } from "apollo-upload-client";

import formDataAppendFile from "apollo-upload-client/public/formDataAppendFile.js";

Ways to require.

const { formDataAppendFile } = require("apollo-upload-client");

const formDataAppendFile = require("apollo-upload-client/public/formDataAppendFile.js");

---

function isExtractableFile

The default implementation for createUploadLink options.isExtractableFile.

Type: ExtractableFileMatcher

Parameter	Type	Description
value	*	Value to check.

Returns: boolean — Is the value an extractable file.

See

• extract-files isExtractableFile docs.

Examples

Ways to import.

import { isExtractableFile } from "apollo-upload-client";

import isExtractableFile from "apollo-upload-client/public/isExtractableFile.js";

Ways to require.

const { isExtractableFile } = require("apollo-upload-client");

const isExtractableFile = require("apollo-upload-client/public/isExtractableFile.js");

---

type ExtractableFileMatcher

A function that checks if a value is an extractable file.

Type: Function

Parameter	Type	Description
value	*	Value to check.

Returns: boolean — Is the value an extractable file.

See

• isExtractableFile has this type.

Examples

How to check for the default exactable files, as well as a custom type of file.

import isExtractableFile from "apollo-upload-client/public/isExtractableFile.js"; const isExtractableFileEnhanced = (value) =>  isExtractableFile(value) ||  (typeof CustomFile !== "undefined" && value instanceof CustomFile);

---

type FetchOptions

GraphQL request fetch options.

Type: object

Property	Type	Description
headers	object	HTTP request headers.
credentials	string?	Authentication credentials mode.

See

• Polyfillable fetch options.

---

type FormDataFileAppender

Appends a file extracted from the GraphQL operation to the FormData instance used as the fetch options.body for the GraphQL multipart request.

Parameter	Type	Description
formData	FormData	FormData instance to append the specified file to.
fieldName	string	Field name for the file.
file	*	File to append. The file type depends on what the ExtractableFileMatcher extracts.

See

• formDataAppendFile has this type.
• createUploadLink accepts this type in options.formDataAppendFile.

---

type ReactNativeFileSubstitute

A React Native File substitute.

Be aware that inspecting network traffic with buggy versions of dev tools such as Flipper can interfere with the React Native FormData implementation, causing multipart requests to have network errors.

Type: object

Property	Type	Description
uri	string	Filesystem path.
name	string?	File name.
type	string?	File content type. Some environments (particularly Android) require a valid MIME type; Expo ImageResult.type is unreliable as it can be just image.

See

• extract-files ReactNativeFileSubstitute docs.
• React Native FormData polyfill source.

Examples

A camera roll file.

const fileSubstitute = {  uri: uriFromCameraRoll,  name: "a.jpg",  type: "image/jpeg", };

Download Details: 
Author: jaydenseric
Source Code: https://github.com/jaydenseric/apollo-upload-client 
License: MIT
#apollo #graphql