MobXをReactNativeで

qiita.com この辺参考

これらいれた。

yarn add babel-plugin-transform-decorators-legacy
yarn add mobx-react
yarn add mobx

.babelrcには追加。

 {
   "presets": ["babel-preset-expo"],
+  "plugins": ["transform-decorators-legacy"],
   "env": {
     "development": {

こんな風にRootStackの上にもできた

import * as React from 'react';
import { StyleSheet, Text, View, Button } from 'react-native';
import { Provider } from 'mobx-react';
import { createStackNavigator } from 'react-navigation';
import { GameScreen } from './Game';
import { DetailScreen } from './Detail';
import MyNumberStore from './stores/MyNumberStore';

const myNumberStore = new MyNumberStore();
const stores = {
  myNumber: myNumberStore,
};

class HomeScreen extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.title}>OikuraPp!</Text>
        <Text>Make a good guess Number !</Text>
        <Button
          title="Start"
          onPress={() => this.props.navigation.navigate('Game')}
        />
        <Button
          title="Settings"
          onPress={() => this.props.navigation.navigate('Details')}
        />
        <Text style={styles.copyright}>(c)shinriyo</Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  title: {
    fontSize: 90,
  },
  copyright: {
    fontSize: 12,
    position: 'absolute',
    bottom: 50
  },
});

const RootStack = createStackNavigator(
  {
    Home: HomeScreen,
    Game: GameScreen,
    Details: DetailScreen,
  },
  {
    initialRouteName: 'Home',
  }
);

export default class App extends React.Component {
  render() {
    // return <RootStack />;
    return (
      <Provider {...stores}>
        <RootStack />
      </Provider>
    );
  }
}

const stores = {
  myNumber: myNumberStore,
};

ここで設定したものが、他の場所のインジェクトしたとこで@inject('myNumber')で使える

@inject('myNumber')
@observer
export class GameScreen extends React.Component<{}> {
  answers: string[] = [];
  myNumber: string = '';