index.js

/**
 * @format
 */

import {AppRegistry} from 'react-native';
import React from 'react';
import Root from './Root';
import {name as appName} from './app.json';
import meiosis from 'meiosis-setup';
import merge from 'mergerino';

const {states, update, actions} = meiosis.mergerino.setup({
  stream: meiosis.simpleStream,
  merge: merge,
  app: {
    initial: {counter: 0},
    Actions: update => ({
      increment: () =>
        update(state => ({...state, counter: state.counter + 1})),
    }),
    services: [],
  },
});

const App = meiosis.react.setup({React, Root});

const app = () => <App states={states} update={update} actions={actions} />;

AppRegistry.registerComponent(appName, () => app);

Root.js

import {
  Button,
  SafeAreaView,
  ScrollView,
  StatusBar,
  StyleSheet,
  Text,
  View,
} from 'react-native';
import {
  Colors,
  DebugInstructions,
  Header,
  LearnMoreLinks,
  ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';

import React from 'react';

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow strict-local
 */

const Root = ({state, actions, update}) => {
  return (
    <>
      <StatusBar barStyle="dark-content" />
      <SafeAreaView>
        <ScrollView
          contentInsetAdjustmentBehavior="automatic"
          style={styles.scrollView}>
          <Header />
          {global.HermesInternal == null ? null : (
            <View style={styles.engine}>
              <Text style={styles.footer}>Engine: Hermes</Text>
            </View>
          )}
          <View style={styles.body}>
            <View style={styles.sectionContainer}>
              <Text style={styles.sectionTitle}>{state.counter}</Text>
              <Button title="Increment" onPress={actions.increment} />
            </View>
          </View>
        </ScrollView>
      </SafeAreaView>
    </>
  );
};

const styles = StyleSheet.create({
  scrollView: {
    backgroundColor: Colors.lighter,
  },
  engine: {
    position: 'absolute',
    right: 0,
  },
  body: {
    backgroundColor: Colors.white,
  },
  sectionContainer: {
    marginTop: 32,
    paddingHorizontal: 24,
  },
  sectionTitle: {
    fontSize: 24,
    fontWeight: '600',
    color: Colors.black,
  },
  sectionDescription: {
    marginTop: 8,
    fontSize: 18,
    fontWeight: '400',
    color: Colors.dark,
  },
  highlight: {
    fontWeight: '700',
  },
  footer: {
    color: Colors.dark,
    fontSize: 12,
    fontWeight: '600',
    padding: 4,
    paddingRight: 12,
    textAlign: 'right',
  },
});

export default Root;