Can I make dynamic styles in React Native?

Say I have a component with a render like this:

<View style={jewelStyle}></View>

Where jewelStyle =

  {
    borderRadius: 10,
    backgroundColor: '#FFEFCC',
    width: 20,
    height: 20,
  },

How could I make the background colour dynamic and randomly assigned? I've tried

  {
    borderRadius: 10,
    backgroundColor: getRandomColor(),
    width: 20,
    height: 20,
  },

But this makes all instances of View have the same colour, I want each one to be unique.

Any tips?

Solution 1:

I usually do something along the lines of:

<View style={this.jewelStyle()} />

...

jewelStyle = function(options) {
   return {
     borderRadius: 12,
     background: randomColor(),
   }
 }

Every time View is rendered, a new style object will be instantiated with a random color associated with it. Of course, this means that the colors will change every time the component is re-rendered, which is perhaps not what you want. Instead, you could do something like this:

var myColor = randomColor()
<View style={jewelStyle(myColor)} />

...

jewelStyle = function(myColor) {
   return {
     borderRadius: 10,
     background: myColor,
   }
 }

Solution 2:

Yes you can and actually, you should use StyleSheet.create to create your styles.

import React, { Component } from 'react';
import {
    StyleSheet,
    Text,
    View
} from 'react-native';    

class Header extends Component {
    constructor(props){
        super(props);
    }    

    render() {
        const { title, style } = this.props;
        const { header, text } = defaultStyle;
        const combineStyles = StyleSheet.flatten([header, style]);    

        return (
            <View style={ combineStyles }>
                <Text style={ text }>
                    { title }
                </Text>
            </View>
        );
    }
}    

const defaultStyle = StyleSheet.create({
    header: {
        justifyContent: 'center',
        alignItems: 'center',
        backgroundColor: '#fff',
        height: 60,
        paddingTop: 15,
        shadowColor: '#000',
        shadowOffset: { width: 0, height: 3 },
        shadowOpacity: 0.4,
        elevation: 2,
        position: 'relative'
    },
    text: {
        color: '#0d4220',
        fontSize: 16
    }
});    

export default Header;

And then:

<Header title="HOME" style={ {backgroundColor: '#10f1f0'} } />

Solution 3:

If you still want to take advantage of StyleSheet.create and also have dynamic styles, try this out:

const Circle = ({initial}) => {


const initial = user.pending ? user.email[0] : user.firstName[0];

    const colorStyles = {
        backgroundColor: randomColor()
    };

    return (
        <View style={[styles.circle, colorStyles]}>
            <Text style={styles.text}>{initial.toUpperCase()}</Text>
        </View>
    );
};

const styles = StyleSheet.create({
    circle: {
        height: 40,
        width: 40,
        borderRadius: 30,
        overflow: 'hidden'
    },
    text: {
        fontSize: 12,
        lineHeight: 40,
        color: '#fff',
        textAlign: 'center'
    }
});

Notice how the style property of the View is set as an array that combines your stylesheet with your dynamic styles.

Solution 4:

The easiest is mine:

<TextInput
  style={[
    styles.default,
    this.props.singleSourceOfTruth ?
    { backgroundColor: 'black' } 
    : { backgroundColor: 'white' }
]}/>