REACT NATIVE FOR REACT DEVELOPERSBarak Cohen, Wondermall

FRONT-END IS BROKEN• Build the same app 3-6 times: iOS

(Phone/Tablet), Android (Phone/Tablet), Web (Desktop/Phone)

• Different teams build the same thing using 3 different languages, frameworks & libraries.

• Hard to maintain feature parity & consistent terminology.

• Impossible to be an expert in all technologies and “own” something in all products

STACK-CENTRIC R&D

iOS

Product Manager

Web Android

iOS Dev

iOS Dev

iOS Dev

Web Dev

Web Dev

Web Dev

Android Dev

Android Dev

Android Dev

BUSINESS-CENTRIC R&D

Feature A

Product Manager

Feature B Feature CFull-Stack

DevFull-Stack

DevFull-Stack

Dev

Full-Stack Dev

Full-Stack Dev

Full-Stack Dev

Full-Stack Dev

Full-Stack Dev

Full-Stack Dev

FULL-STACK IS HARD!• Almost all devs at Wondermall do Python,

ObjC+Swift and AngularJS

• Level of expertise vary. No one is a rock star on all 3 platforms

• We’ll never get everyone cross trained on Android, Windows Phone, Apple Watch, Apple TV, …

• If we want to remain Full Stack, we’ll have to rethink our strategy

Powered by React-Native

BASICS

REACT-NATIVE IS…• JavaScript for Application Logic

• Native UI (No WebViews)

• Flexbox Layout

• Polyfills (fetch API) & Platform APIs (Camera)

• Compatible with nearly all React and JS libs

GETTING STARTED

$ brew install node && brew install watchman

$ npm install -g react-native-cli

$ react-native init MyProject && cd MyProject

$ react-native run-ios

HELLO WORLDvar React = require('react')var { View, Text } = require('react-native')

class HelloWorldView extends React.Component { render() { return ( <View><Text>Hello World</Text></View> ) }}

React DOM React Native

React

React Canvas

React Three

iOS Android macOS Win 10 Web

REACT ECO-SYSTEM

Tizen

REACT (NATIVE+JS) BENEFITS

• “Learn once write anywhere”

• Reuse almost all non-UI code across all platforms

• Reuse most UI code between Native Platforms

• Hot-reloading JS, debug in Chrome

BENEFITS - CON’T• Can be added incrementally to an

existing app

• Over-the-wire updates w/o AppStore (AppHub)

• JS w/ ES6 is succinct and productive

• Can use previously written native code and UI

STYLE & LAYOUT

ADDING STYLEclass HelloWorldView extends React.Component { ...

render() { return ( <View style={{padding: 10}}> <Text style={{fontSize: 14, color: '#0000ff'}}> Hello World </Text> </View> ) }}

FLEXBOX LAYOUTclass HelloWorldView extends React.Component { render() { return ( <View style={{flexDirection: 'column', flex: 1}}> <View style={{flex: 1, backgroundColor: 'red'}}></View> <View style={{flex: 1, backgroundColor: 'green'}}></View> <View style={{flex: 1, backgroundColor: 'blue'}}></View> </View> ) }}

FLEXBOX LAYOUT - 2class HelloWorldView extends React.Component { render() { return ( <View style={{flexDirection: 'row', flex: 1}}> <View style={{flex: 1, backgroundColor: 'red'}}></View> <View style={{flex: 1, backgroundColor: 'green'}}></View> <View style={{flex: 1, backgroundColor: 'blue'}}></View> </View> ) }}

NATIVE APISimport React, { Component } from 'react';import { MapView } from 'react-native';

class MapMyRide extends Component { render() { return ( <MapView style={{height: 200, margin: 40}} showsUserLocation={true} /> ); }}

ROUTING

return ( <Navigator initialRoute={{ title: 'My Initial Scene', index: 0 }} renderScene={(route, navigator) => <MyScene title={route.title} onForward={ () => { navigator.push({ title: 'Scene ' + route.index + 1, index: route.index + 1, }); }} /> } /> )

BUILT-IN

REACT-NATIVE-ROUTER-FLUX

import { PageOne, PageTwo } from './Pages';

export default class App extends Component { render() { return ( <Router> <Scene key="root"> <Scene key="pageOne" component={PageOne} title="PageOne" initial={true} /> <Scene key="pageTwo" component={PageTwo} title="PageTwo" /> </Scene> </Router> ) }}

UNIVERSAL APPS

Shared - Native & WebRedux / Relay

API Client

Business Logic

Shared Native

Native Specific<TabBarIOS>,

<AndroidToolbar>

<Text>, <TextInput>, <Image>

Web<div>

Business Level Comp’

<span>

<img>

DEBUGGING & TOOLING

• Reload - Clears all JS code and resets the state

• Remote JS Debugging - Chrome / VSCode with breakpoints and Console (no network)

• Live Reload - Automatic Reload (as above)

• Hot Reloading - Change JS code without resetting the state

DEVELOPER MENU

REDUX REMOTE DEV TOOLS

PACKAGER• Built-in packager with ES6 support

• Development: local webserver serves the bundled JS

• Production:

• Use .ios.js or .android.js suffixes, Packager will include the correct file for the platform bundle

$ react-native bundle —platform ios

OTA UPDATES• Updates JS & assets without AppStore

submission

• Apple’s policy allows it for fixes & minor improvements

• Microsoft CodePush - Commercial

• AppHub - Hosted / OSS

INTEGRATION & INTERNALS

NATIVE VS. JAVASCRIPTView ControllerView ControllerView Controller Bridge

(incl. JS VM)

JavaScript FileJavaScript FileJavaScript File

RCTRootViewUIView

UIView

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions…{ NSURL *jsCodeLocation = @“http://localhost:8081/index.ios.bundle?platform=ios";

RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation moduleName:@"MyComponent" initialProperties:@{} launchOptions:launchOptions];

UIViewController *rootViewController = [[UIViewController alloc] init]; rootViewController.view = rootView;

self.window.rootViewController = rootViewController; [self.window makeKeyAndVisible];}

MULTIPLE RCTROOTVIEWS

RCTRootViewUIView

UIView

RCTRootViewUIView

UIView

Bridge(incl. JS VM)

{ // AppDelegate didFinishLaunchingWithOptions self.bridge = [[RCTBridge alloc] initWithBundleURL:@"localhost..." moduleProvider:nil launchOptions:nil]

// When you want to show R/N view [[RCTRootView alloc] initWithBridge:self.bridge moduleName:"MyComponent"];

// Somewhere else [[RCTRootView alloc] initWithBridge:self.bridge moduleName:"MyOtherComponent"];

}

NATIVE MODULES• Export native functions to be called

from JS

• Export constants and enums

• Send events to JS from native

• They are singletons

// CalendarManager.h#import "RCTBridgeModule.h"

@interface CalendarManager : NSObject <RCTBridgeModule>@end

// CalendarManager.m@implementation CalendarManager

RCT_EXPORT_MODULE();

RCT_EXPORT_METHOD(addEvent:(NSString *)name location:(NSString *)location){ RCTLogInfo(@“Creating event %@ at %@", name, location);}

@end

RETURN VALUE W/ PROMISES

RCT_EXPORT_METHOD(findEvents, resolver:(RCTPromiseResolveBlock)resolve rejecter:(RCTPromiseRejectBlock)reject){ NSArray *events = ... if (events) { resolve(events); } else { NSError *error = ... reject(@"no_events", @"There were no events", error); }}

import { NativeModules } from ‘react-native';

CalendarManager = NativeModules.CalendarManager;

CalendarManager.addEvent(‘Birthday Party’, …);

async function updateEvents() {try { var events = await CalendarManager.findEvents();

this.setState({ events });} catch (e) { console.error(e);}

}

updateEvents();

MISC.

PERFORMANCE TIPS• Minimize bridge messages

• Implement shouldComponentUpdate

• Direct Manipulation with setNativeProps

• Rewrite in Native

FURTHER READING• Facebook’s F8 App -

http://makeitopen.com/

• React Native Newsletter - http://reactnative.cc/

• Practice layout and Flexbox https://github.com/jondot/ReactNativeKatas

• https://github.com/jondot/awesome-react-native

STARTER KITS

• Native Starter - http://startreact.com/themes/native-starter/

• Ignite - https://github.com/infinitered/ignite

• este.js - https://github.com/este/este

3RD-PARTY COMPONENTS

• https://js.coach/react-native/

• https://react.parts/native

• nativebase.io

THANK YOU!(QUESTIONS?)