React native cheat sheet with things that I find interesting or I had to google/figure out
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README.md

Since I just started playing around with React Native and there are just few resources available online I've decided to created this repo to write down things that I find interesting or I've spent some time googling/figuring out. Hope it helps and makes your time with React Native even more fun!

And of course, feel free to contribute

How to add custom fonts to a React Native app in Xcode

  1. Create a new group Fonts within your Xcode project
  2. Drag and drop fonts from Finder to the Fonts group you just created, and check your project name in Add to targets list
  3. Expand your project name folder within the main directory in your project and open Info.plist
  4. Add Fonts provided by application as a new key
  5. Add a new item named after the full font name with extension under Fonts provided by application for each font you've added to the fonts folder
  6. Run Shift + Command + K to clean last build
  7. Then Command + B to start a new build
  8. And finally Command + R to run the application

If you still see the error Unrecognized font family restart your react packager or add the following to the AppDelegate.m in order to print all available fonts: NSLog (@"Font families: %@", [UIFont familyNames]);

How to use it

var styles = React.StyleSheet.create({
  title: {
    color: '#000',
    fontFamily: 'Font-Name-Without-Extension'
  }
});

How to make circle image with React Native

Since borderRadius style expects number as a value you can't use borderRadius: 50%. To make circle all you have to do is use your image width/height and devide it with 2.

Example for 100x100 image:

// component
<Image style={styles.image} source={{uri: 'http://placehold.it/100x100'}}/>
// styles
var styles = StyleSheet.create({
  image: {
    height: 100,
    borderRadius: 50,
    width: 100
  }
});

React Native Image component can have child components

Because of HTML and <img /> tag it's easy to ignore that React <Image/> component can have child components, but it can.

This is how you can do it. If it doesn't look pretty, change image source and add styles to make it nicer!

<Image source={{uri: 'http://placehold.it/300x300'}}>
  <Image source={{uri: 'http://placehold.it/100x100'}}/>
  <Text>This is my text</Text>
</Image>

Text transform uppercase with React Native styles

I wasn't able to find react native style that does CSS text-transform: uppercase;. To make my <Text> component uppercased I've used javascript fallback.

<Text style={styles.published}>{this.props.myText.toUpperCase()}</Text>

React Native Text component numberOfLines default value

Number of lines expects integer to be passed in as specified in docs.

I've tried using null and it works but it logs warning in console: numberOfLines expects number not null. Searching react repo for numberOfLines didn't help and I just tried out setting it to 0 and it worked out without any wornings.

Example component that is showing just first 10 lines of text and on tap shows the rest.

class Article extends Component {
  constructor() {
    super();

    this.state = {
      // initial number of lines
      numberOfLines: 10
    }
  }

  render() {
    var showMore = this.state.numberOfLines ? <Text style={{color: '#f00'}}>{'SHOW MORE \u25BC'}</Text> : null;

    return (
      <ScrollView>
        <TouchableHighlight onPress={() => this.setState({numberOfLines:0})} >
          <View>
            <Text numberOfLines={this.state.numberOfLines}>{this.props.whateverLongText.youHave}</Text>
            {showMore}
          </View>
        </TouchableHighlight>
      </ScrollView>
    );
  }
}

Get device width and height

There are quite a few ways to do this, but an easy to use module is react-native-device

npm install react-native-device --save

Then, to use in your project:

var Device = require('react-native-device');
    
if (Device.isIpad()) {
  // return iPad layout
  } else {
  // return iPhone layout
}

var deviceWidth = Device.width() // return device width
var deviceHeight = Device.height() // return device width

var deviceKind = Device.kind() // returns kind of device (iPad, iPhone4, iPhone6, etc...)

Extending and overriding styles with inline styles and how to use dynamic styles

If you want to override one/more styles defined within React.StyleSheet.create you can do it inline. Instead of using style={styles.myStyle} you can pass in array of style properties:

<View style={[ styles.myStyle, {color:'red'}, {something: 'else'} ]} />

<Text style={[ styles.myText, {width: Device.width} ]} />

Preventing Image Flash after ActionSheetIOS is used

Sometimes after a user has shared something on your app via the ActionSheetIOS component, images that were previsouly displayed in your app will disappear for a moment before getting re-rendered, causing a flicker. To prevent this you can set the Image's defaultSource to the main source.

<Image accessibilityLabel='x-icon' style={styles.xIcon} source={requireImage('x-icon')} defaultSource={requireImage('x-icon')} />