my_text.js

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

var MY_TEXT_REF = "MyText"

class MyText extends React.Component {
    static propTypes = {
        bold: React.PropTypes.bool,
        children: React.PropTypes.node,
        style: React.PropTypes.instanceOf(StyleSheet),
    }

    static defaultProps = {
        bold: false,
    }

    setNativeProps(props: Object) {
        this.refs[MY_TEXT_REF].setNativeProps(props);
    }

    defaultTextStyle() {
        if(this.props.bold)
            return styles.bold;
        else
            return styles.regular;
    }

    render() {
        return (
            <Text ref={MY_TEXT_REF} style={[this.defaultTextStyle(), this.props.style]}>{this.props.children}</Text>
        );
    }
}

var styles = StyleSheet.create({
    regular: {
        fontFamily: 'Montserrat',
    },

    bold: {
        fontFamily: 'Montserrat-Bold',
    },
});

module.exports = MyText;