DynamicType in React Native

DynamicType.h

#import <Foundation/Foundation.h>
#import "RCTBridgeModule.h"

@interface DynamicType : NSObject <RCTBridgeModule>

@end

DynamicType.m

#import "DynamicType.h"
#import <UIKit/UIKit.h>

@implementation DynamicType

RCT_EXPORT_MODULE();

- (NSDictionary *)constantsToExport {
  
    NSDictionary *dynamicSizes = @{ @"Headline"     : @([UIFont preferredFontForTextStyle:UIFontTextStyleHeadline].fontDescriptor.pointSize),
                                    @"Subheadline"  : @([UIFont preferredFontForTextStyle:UIFontTextStyleSubheadline].fontDescriptor.pointSize),
                                    @"Body"         : @([UIFont preferredFontForTextStyle:UIFontTextStyleBody].fontDescriptor.pointSize),
                                    @"Caption1"     : @([UIFont preferredFontForTextStyle:UIFontTextStyleCaption1].fontDescriptor.pointSize),
                                    @"Caption2"     : @([UIFont preferredFontForTextStyle:UIFontTextStyleCaption2].fontDescriptor.pointSize),
                                    @"Footnote"     : @([UIFont preferredFontForTextStyle:UIFontTextStyleFootnote].fontDescriptor.pointSize)};
  
  return dynamicSizes;
}

@end

example.ios.js

/* @flow */
'use strict';

var React = require('react-native');
var DynamicType = require('NativeModules').DynamicType;

var {
  StyleSheet,
  View,
  Text
} = React;

var SampleComponent = React.createClass({

    render: function() {
        return (
            <View style={styles.container}>
                <Text style={[styles.message, {fontSize: DynamicType.Headline}]}>Headline</Text>
                <Text style={[styles.message, {fontSize: DynamicType.Subheadline}]}>Sub</Text>
                <Text style={[styles.message, {fontSize: DynamicType.Body}]}>Body</Text>
                <Text style={[styles.message, {fontSize: DynamicType.Caption1}]}>Cap1</Text>
                <Text style={[styles.message, {fontSize: DynamicType.Caption2}]}>Cap2</Text>
                <Text style={[styles.message, {fontSize: DynamicType.Footnote}]}>Footnote</Text>
            </View>
        );
    }
});

var styles = StyleSheet.create({

	container: {
		flex: 1,
		backgroundColor: 'red',
        	justifyContent: 'center'
	},

    message: {
        textAlign: 'center'
    }
});