React Native for Better Apps

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February 23, 2017

React Native for Better Apps

React Native rende possibile utilizzare gli stessi paradigmi di React per scrivere applicazioni mobile per iOS e Android con UI nativa. Con Gian Marco Toso parleremo di React Native e delle sue potenzialità, di come inizializzare un’applicazione e di quali tecniche utilizzare per strutturarla al meglio!



February 23, 2017


  1. 1.

    It (mostly) just works! React Native for Better Apps Gian

    Marco Toso @gianmarcotoso gianmarcotoso Software Engineer, The One Who Knocks
  2. 2.

    About Me Software Engineer from Turin, Italy MSc in Computer

    Engineering Researcher and Freelancer
  3. 3.

    About My Stack Docker PHP/Laravel "It was working on my

    machine!" The monolith is here to stay NodeJS/TypeScript Seriously, it's awesome! React + Redux The Flux Capacitor! (formerly) iOS/ObjectiveC and I still get nightmares
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    Native Applications A nightmare to develop A lot of devices

    A lot of resolutions Different operating systems with different rules Different programming languages
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    Hybrid Applications Write Once, Run Anywhere! One language (JavaScript) One

    runtime environment (the WebView) Less than ideal UI performance
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    React Native UI written with ReactJS Modern JavaScript Code Native

    extensions are bridged to JavaScript UI Components are mapped to native components Apps written with React Native are real native apps!
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    An Example import React from 'react' import { View, Text,

    AppRegistry } from 'react-native' class HelloWorld extends React.Component { render() { return ( <View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}> <Text style={{fontSize: 72}}>Hello, World!</Text> </View> ) } } AppRegistry.registerComponent('app', () => HelloWorld)
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    CLI Tool React Native comes with a command line utility

    that can be installed with `yarn install react-native-cli` The CLI tool can be used to create new projects (`react- native init`) or to run them (`react-native run-*`) In order to run a React Native project on a specific platform, you'll need to have the proper SDK installed!
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    Styling Inline Styles Flexbox Algorithm CSS-Like syntax Styles can be

    defined as POJOs Styles should be defined using the StyleSheet class
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    An Example import React from 'react' import { View, Text,

    StyleSheet } from 'react-native' const styles = StyleSheet.create({ container: { flex: 1, justifyContent: 'center', alignItems: 'center' }, titleText: { fontSize: 72 }, red: { color: 'red' } }) const HelloWorld = () => ( <View style={styles.container}> <Text style={[styles.titleText,]}>Hello, World!</Text> </View> ) export default HelloWorld
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    Built-in Components React Native has many built-in component to handle

    common operations Most components are compatible with both supported platforms
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    TouchableHighlight The TouchableHighlight component allows anything to be able to

    handle touch events Can be used to wrap most components Exposes an `onPress` method that receives an Event Handler
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    TouchableHighlight import React from 'react' import { TouchableHighlight, View, Image,

    Text } from 'react-native' class TouchableCard extends React.Component { handleCardTouch = () => { this.props.onCardTouched() } render() { return ( <View> <TouchableHighlight onPress={this.handleCardTouch}> <View> <Image source={require('image.png')} /> <Text>Some Fancy Image</Text> </View> </TouchableHighlight> </View> ) } } export default TouchableCard
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    Modals The Modal component can wrap a View and all

    its content and present it modally whenever required A Modal will become visible as soon as its visible prop becomes true, and will disappear when it becomes false It's possible to change the animation used to show the modal by setting the animationType to either fade, slide or none
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    Modals import React from 'react' import { View, Modal, Text,

    Button } from 'react-native' class ModalContainer extends React.Component { state = { isModalVisible: false } render() { <View> <Modal visible={this.state.isModalVisible}> <View> <Text>Hello, Modal!</Text> <Button title="Bye" onPress={() => this.setState({isModalVisible: false})} /> </View> </Modal> <Button title="Open Modal" onPress={() => this.setState({isModalVisible: true})} /> </View> } }
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    StatusBar The StatusBar component allows to configure the behavior of

    the mobile OS' status bar It can be included in any screen in order to have different styles for different pages
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    StatusBar import React from 'react' import { StatusBar, View }

    from 'react-native' class MyFancyPage extends React.Component { render() { return ( <View> <StatusBar barStyle="light-content" /> <View> {/* Page content... */} </View> <View> ) } }
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    ListView The ListView component allows to create scrollable views containing

    items of the same type The component uses a DataSource to populate itself on every render It also uses a callback to decide how to render each row, and it's highly configurable
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    ListView class MyComponent extends Component { constructor() { super() const

    ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2}) this.state = { dataSource: ds.cloneWithRows(['row 1', 'row 2']) }; } render() { return ( <ListView dataSource={this.state.dataSource} renderRow={(rowData) => <Text>{rowData}</Text>} /> ); } }
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    Navigation The Navigator Component allows to handle navigation Navigation is

    handled through the use or routes and a navigation stack. When a route is matched, a specific component is returned. Navigation is handled through the use or routes and a navigation stack.
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    Navigation const routes = [ { key: 'home', title: 'Home

    Screen', component: (p) => <Home {...p} /> }, { key: 'login', title: 'Login', component: (p) => <Login {...p} /> }, ] const Home = ({navigator}) => ( <Button onPress={() => navigator.push('login')} title="Login" /> ) const renderRoute = (route, navigator) => ( routes.find(r => r === route.key) .component({navigator}) ) const NavigationStack = () => ( <Navigator initialRoute={routes[0]} renderScene={renderRoute} /> ) export default NavigationStack
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    NavigationBar The Navigator.NavigationBar allows to create a Navigation Bar, persistent

    across scenes It allows to define the Left and Right buttons behavior, as well as the Title
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    NavigationBar import React from 'react' import { Navigator, Text, Button

    } from 'react-native' const LeftButton = (route, navigator, index, navState) => ( <Button title="Back" onPress={() => navigator.pop()} /> ) const RightButton = (route, navigator, index, navState) => {} const Title = (route, navigator, index, navState) => ( <Text>{route.title}</Text> ) const Navbar = () => ( <Navigator.NavigationBar routeMapper={{ LeftButton, RightButton, Title }} /> ) // Passed to the `navigationBar` prop of the `Navigator` export default Navbar
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    Navigation The Navigator Component is less than ideal Configuring navigation

    this way is hard, cumbersome and error prone You need a way to pass the `navigator` object around if you want to do anything useful The Navigator component is being deprecated, along with its newer alternative NavigatorExperimental The official recommended replacement is a third party library called React Navigation
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    Built-in Modules React Native has many built-in modules to handle

    operations common to mobile devices Most modules are compatible with both supported platforms Module actions are called imperatively
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    Vibration The Vibration module makes the phone vibrate using the

    specified pattern. The pattern can be repeated any number of times import { Vibration } from 'react-native' Vibration.vibrate( [0, 100], // pattern 1 // repeat )
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    Alert The Alert module shows a popup dialog box with

    confirmation buttons Each button can have an `onPress` event handler import { Alert } from 'react-native' Alert.alert( 'Confirm?' 'Do you confirm this action?', [ { title: 'Yes', onPress: () => {} }, { title: 'No', onPress: () => {}, style: 'cancel' }, ] )
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    AppState The AppState module tells us if the app is

    in the background, foreground or inactive state. It can be listened to by using the addEventListener method import { AppState } from 'react-native' let state = 'background' AppState.addEventListener('change', (newState) => { state = newState })
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    Dimensions Sometimes it can be useful to know the dimensions

    of either the screen or the window. The Dimensions module comes to our aid, by allowing to read dimensions at any time import { Dimensions } from 'react-native' const { height, width } = Dimensions.get('window') const myStyle = { height, width } const myComponent = ({children}) => <View style={myStyle}>{children}</View> // This will soon be possible (not yet!): Dimensions.addEventListener('change', ({window, screen}) => { console.log('new dimensions:', window, screen) })
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    JavaScript Ecosystem A React Native app's code is written in

    JavaScript This means you can use most of the libraries you're used to! Redux Axios Fetch LocalForage Lodash RxJS
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    Third Party Components You'll find many third-party libraries and components

    online Some are even recommended by the React Native core team, like AirBnB's ` ` react-native-maps
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    Animations Animations are a big part of a Mobile Application's

    UX React Native makes animating components somewhat easy with the Animated module
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    Animations The Animated module exposes replacement components View, Image and

    Text These components' style prop can receive instances of the Animated.Value class instead of regular numbers Animation functions such as timing or spring can be used to animate Animated.Values smoothly
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    Animations import React from 'react' import { Text, Animated, Easing

    } from 'react-native' const _opacity = new Animated.Value(1) const changeOpacity = (value = 0) => { Animated.timing({ toValue: value, delay: 1000, easing: Easing.inOut(Easing.ease) }).start( () => changeOpacity((value + 1) % 2) ) } class Wobble extends React.Component { componentDidMount = () => changeOpacity() render() { return ( <Animated.View style={{opacity: _opacity}}> <Text>Wobble!</Text> </Animated.View> ) } } export default Wobble
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    React Native Web Third-party library to render React Native apps

    inside a web browser Maps React Native's primitives to standard HTML tags Allows to debug an App in the browser where possible - there is no support for mobile-specific functionalities! Not really production ready
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    React Native Windows Third party module that allows to deploy

    React Native apps on the Universal Windows Platform Maps React Native components to native C# primitives Still under development, YMMV