Mobx Basic Setup

.babelrc

{
  "presets": ["react-native"],
  "plugins": ["transform-decorators-legacy"]
}

App.js

import React, { Component } from 'react';
import {
  View
} from 'react-native';
import { Provider } from 'mobx-react';
import HomeScreen from './screens/HomeScreen'
import store from './store';

export default App = () => (
  <Provider appStore={store}>
    <HomeScreen></HomeScreen>
  </Provider>
)

HomeScreen.js

import React, { Component } from 'react';
import {
  View
} from 'react-native';
import Modal from 'react-native-modal';
import { observer, inject } from "mobx-react";]
import { Screen } from './../shared'

// Use inject from any Component to connect on the store
@inject("appStore") @observer
class HomeScreen extends Component {
  
  toggleModal = () => {
    const { appStore } = this.props;
    appStore.set('isModalVisible', !appStore.get('isModalVisible'));
  }

  render() {
    const isModalVisible = this.props.appStore.get('isModalVisible');
    return (
      <Modal isVisible={isModalVisible}>
        <View><View/>
      </Modal>
    );
  }
}

export default HomeScreen;

store.js

import { observable } from 'mobx';

const initialState = {
  isModalVisible: false
}

export default observable.map(initialState);