Building WhatsApp in a Day with React Native

@VladimirNovick

Software architect & consultant

Web / Mobile / VR / AR / IoT / AI

vnovick.com

 author, engineer, enterpreneur

@VladimirNovick

vnovick.com

CTO & Co-founder

creating a robust, performant, and feature-rich online conferencing experience

http://eventloop.app

@EventLoopHQ

Assumptions

  • You are familiar with JavaScript and Web development
  • You are familiar with basics of React
  • You are interested in React Native

You did initial setup sent over by email and have Hello World app running

Why React native?

  • Amazing DX close to Web development
  • Shared codebase
  • NPM/Yarn, bundlers, modern JS/Typescript, State management

The idea

React Native combines the best parts of native development with React. You can use React Native today in your existing Android and iOS projects or you can create a whole new app from scratch.

  • Written in JavaScript—rendered with native code
  • Easy to write native code and integrate in React Native app
  • Get updates instantly with Fast refresh

Motivation

  • Code reuse between platforms
  • Smaller dev team is able to handle multiple platforms (Android/iOS/Web)
  • Shared logic and ecosystem
  • Declarative and more functional programming style
  • Styling using modern CSS techniques in mobile apps

Architecture

React

JavaScript

JSC

Bridge

Shadow tree

JSON

Native Modules

Native

Threading model

  • UIManager Thread - Responsible for the native side.
    • The main thread where app is running.
    • Has access to UI
  • JS Thread - Run all bundled main.bundle.js file
  • Shadow Thread - Does the whole recalculation
  • Native modules thread - platform apis

Execution flow

Start

Main Thread

load .js bundles and send to JS thread

React

Reconciler generates new VDOM layout

JS Thread

layout calculations

using Yoga

UI

updates

Shadow thread

Native modules

React Native re-architecture

https://t.co/wDaXRvLtlA?amp=1

How to get started

https://reactnative.dev/docs/environment-setup

npx react-native init WhatsappProject

Debugging

https://fbflipper.com/

https://github.com/jhen0409/react-native-debugger

Errors and warnings

Errors and warnings

Yellow and Red boxes are disabled in production

To disable them in development:

Application layout

/android - folder that stores Android native code

/ios - folder that stores Android native code

app.json - simulates Expo like config. Basically is imported by  index.js

index.js - Entry point of application

AppRegistry registers app with native modules

React Native components

https://reactnative.dev/docs/components-and-apis#basic-components

Excercise 1

Create Screens

Clone the repo:

Follow the instructions for Excercise 1 in the Readme.md

https://github.com/vnovick/whatsapp_workshop_2020

Styling in React Native

Style names and values usually match how CSS works (except transforms) except instead of kebab-case using camelCase.

https://reactnative.dev/docs/stylesheet

Flexbox

container: {

  flex: 1,

},

box1: {

  flex: 1,

  backgroundColor: 'red',

},

 

<View style={styles.container}>

  <View style={styles.box1} />

</View>

container: {

  flex: 1,

},

box1: {

  flex: 1,

  backgroundColor: 'red',

},

box2: {

  flex: 1,

  backgroundColor: 'orange',

},

 

<View style={styles.container}>

  <View style={styles.box1} />

  <View style={styles.box2} />

</View>

container: {

  flex: 1,

},

box1: {

  flex: 1,

  backgroundColor: 'red',

},

box2: {

  flex: 2,

  backgroundColor: 'orange',

},

 

<View style={styles.container}>

  <View style={styles.box1} />

  <View style={styles.box2} />

</View>

Flexbox

container: {

  flex: 1,

},

box1: {

  flex: 1,

  backgroundColor: 'red',

},

box2: {

  flex: 2,

  backgroundColor: 'orange',

},

 

<View style={styles.container}>

  <View style={styles.box1} />

  <View style={styles.box2} />

</View>

flex-direction establishes the main axis

In React Native default flex-direction is column

Excercise 2

Style screen Layout

Continue from Excercise 1 solution

Clone step1 branch in the same repo

Follow the instructions for Excercise 2 in the Readme.md

or

Images

https://reactnative.dev/docs/images

Static resources can be auto sized

Dynamic resources need to have size provided

Image resize modes

<Image

  style={{

    width: 51,

    height: 51,

    resizeMode: Image.resizeMode.contain,

  }}

  source={{

    uri:'data:image/png;base64,iVBORw0KGg...',

  }}

/>

cover - will take max value of either width or height and scale uniformly (maintain aspect ratio)

contain - will take min value of either width or height and scale uniformly (maintain aspect ratio)

Image resize modes

stretch - scale width and height independently without conforming to aspect ratio

repeat - repeat the image to cover the frame of the view. image will keep size and aspect ratio

Icons - Android

react-native-vector-icons

rm -rf android/app/build

https://github.com/oblador/react-native-vector-icons#option-with-gradle-recommended

<Icon

  name="chat"

  color="#fff"

  size={23}

  style={{ padding: 5 }}

/>

Icons - iOS

react-native-vector-icons

rm -rf android/ios/build

https://github.com/oblador/react-native-vector-icons#option-with-cocoapods

add to Info.plist

	<key>UIAppFonts</key>
	<array>
	<string>AntDesign.ttf</string>
	<string>Entypo.ttf</string>
	<string>EvilIcons.ttf</string>
	<string>Feather.ttf</string>
	<string>FontAwesome.ttf</string>
	<string>FontAwesome5_Brands.ttf</string>
	<string>FontAwesome5_Regular.ttf</string>
	<string>FontAwesome5_Solid.ttf</string>
	<string>Foundation.ttf</string>
	<string>Ionicons.ttf</string>
	<string>MaterialIcons.ttf</string>
	<string>MaterialCommunityIcons.ttf</string>
	<string>SimpleLineIcons.ttf</string>
	<string>Octicons.ttf</string>
	<string>Zocial.ttf</string>
	</array>
</dict>

<Icon

  name="chat"

  color="#fff"

  size={23}

  style={{ padding: 5 }}

/>

Dimensions

https://reactnative.dev/docs/usewindowdimensions

Lists

Exercise 3

Continue styling

Continue from Excercise 2 solution

Clone step2 branch in the same repo

Follow the instructions for Excercise 3 in the Readme.md

or

Networking

Input and Keyboard

Exercise 4

API and Input 

Continue from Excercise 3 solution

Clone step3 branch in the same repo

Follow the instructions for Exercise 4 in the Readme.md

or

Navigation setup

npm install @react-navigation/native
npm install react-native-reanimated react-native-gesture-handler react-native-screens react-native-safe-area-context @react-native-community/masked-view
npx pod-install ios

https://reactnavigation.org/docs/getting-started

Stack Navigator

npm install @react-navigation/stack

Instead specifying component you can use render callback

Navigating

Passing params

Second argument passed to navigate will be accessible on route.params inside screen component

You can also pass initialParams to a screen

Screen can update its params by using 

navigation.setParams

More on params: https://reactnavigation.org/docs/params

Navigation Headers

Configuring headers: https://reactnavigation.org/docs/headers

Changing Header buttons:

https://reactnavigation.org/docs/header-buttons

Exercise 5

Navigation

Continue from Excercise 4 solution

Clone step4 branch in the same repo

Follow the instructions for Exercise 5 in the Readme.md

or

Animations

Create animated value

Create custom Animated component or use Animated.View

Animations

Add animated value as style

Trigger animation

Interpolate on value if needed

Exercise 6

Animations

Continue from Excercise 5 solution

Clone step5 branch in the same repo

Follow the instructions for Exercise 6 in the Readme.md

or

GraphQL

A query language for your API

How does it look like

How does it look like

GraphQL SDL

https://graphql.org/learn/schema/

type Post {

   title: String!

   content: String!

   user: User!

}

type Person {

    name: String!

    address: String

    posts: [Post!]!

}

GraphQL SDL

https://graphql.org/learn/schema/

type Post {

   title: String!

   content: String!

   user: User!

}

type Person {

    name: String!

    address: String

    posts: [Post!]!

}

GraphQL Resolvers

https://graphql.org/learn/execution/#root-fields-resolvers

What about GraphQL client?

https://www.apollographql.com/docs/react/get-started/

import {ApolloClient, InMemoryCache, split, HttpLink} from '@apollo/client';
import {getMainDefinition} from '@apollo/client/utilities';
import {WebSocketLink} from '@apollo/client/link/ws';

// Create an http link:
const httpLink = new HttpLink({
  uri: 'endpoint url',
});

// Create a WebSocket link:
const wsLink = new WebSocketLink({
  uri: 'endpoint url',
  options: {
    reconnect: true,
  },
});

// The split function takes three parameters:
//
// * A function that's called for each operation to execute
// * The Link to use for an operation if the function returns a "truthy" value
// * The Link to use for an operation if the function returns a "falsy" value
const splitLink = split(
  ({query}) => {
    const definition = getMainDefinition(query);
    return (
      definition.kind === 'OperationDefinition' &&
      definition.operation === 'subscription'
    );
  },
  wsLink,
  httpLink,
);

const cache = new InMemoryCache();
const client = new ApolloClient({
  // Provide required constructor fields
  cache: cache,
  link: splitLink,
});

export default client;

Executing subscriptions and mutations

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

const GET_MESSAGES_BY_ID = gql`
  subscription getMessagesById($conversationId: uuid) {
    messages(where: {conversation_id: {_eq: $conversationId}}) {
      id
      message
      userId: user_id
    }
  }
`;

const POST_MESSAGE = gql`
  mutation postMessageForUserId(
    $userId: uuid
    $conversationId: uuid
    $message: String!
  ) {
    insert_messages(
      objects: {
        user_id: $userId
        conversation_id: $conversationId
        message: $message
      }
    ) {
      returning {
        message
      }
    }
  }
`;



///
//
export const ChatViewScreen = ({navigation}) => {
  const {id: conversationId} = route.params;
  const {loading, data, error} = useSubscription(GET_MESSAGES_BY_ID, {
    variables: {conversationId},
  });

  const [postMessage, {data: mutationData}] = useMutation(POST_MESSAGE);
  
  
  <Compose
  submit={(message) =>
  postMessage({
    variables: {
      userId: MY_USER,
      conversationId,
      message,
    },
  })
}
/>

Exercise 7

GraphQL and realtime

Continue from Excercise 6 solution

Clone step6 branch in the same repo

Follow the instructions for Exercise 7 in the Readme.md

or

Thank you

@VladimirNovick