React native and MobX: How to create a global store?

Question

I am currently trying to implement a mobx storage which I can call from everywhere like so:

import {userStore} from '../UserStore.js';

At the end of the file, my export functionality looks as follows:

const userStore = new UserStore();
export {userStore};

As I understand, everytime I call the import functionality, the object gets re-created with which multiple files that import UserStore don't share the same variables.

However, I want that every file that imports UserStore imports the same object with the exact same variables. How can I achieve this? I am not fully sure how to achieve, so any ideas and examples would be appreciated :)

The full code (for the UserStore.js declaration), if of any help, is as follows (look at the very bottom for the export statement)

import {observable, computed, action} from 'mobx';
import {ObservableMap, toJS} from 'mobx';
import {Fb} from './firebase.js';

class UserStore {

  /** GPS */
  @observable usrLng = 0.0;
  @observable usrLat = 0.0;
  @observable watchID = null;

  @action
  watchCurLocation() {
    this.watchID = navigator.geolocation.watchPosition((position) => {
      console.log("Recording GPS data from within the Store!!");
      this.usrLat = parseFloat(position.coords.latitude);
      this.usrLng = parseFloat(position.coords.longitude);
      }, (error) => console.log(JSON.stringify(error)), {
        enableHighAccuracy: true,
        timeout: 2000,
        maximumAge: 1000
      });
  }

  @action
  clearWatch() {
    navigator.geolocation.clearWatch(this.watchID);
  }
  /*/ GPS */

  /** BIKE BOOKING  */
  @observable interestBikeNo = -1;
  @observable bookedBikeNo = -1;

  @action
  setInterestBikeNo(bn) {
    this.interestBikeNo = bn;
  }

}

const userStore = new UserStore();
export {userStore};

Answer 1

You simply need a singleton instance of UserStore class

Sample demo

let localInstance = null;

export class Apple {
  static newInstance() {
    if (! localInstance)
      localInstance = new Apple();
    return localInstance;
  }
}

// usage

import {Apple} from './apple';
const instance = Apple. newInstance();

In your case, you can use a simple function

import {observable, computed, action} from 'mobx';
import {ObservableMap, toJS} from 'mobx';
import {Fb} from './firebase.js';

class UserStore {
  // omitted
}

let userStore;
export function getUserstore() {
  if (!userStore)
    userStore = new UserStore();
  return userStore;
};

Somewhere in code

// instead of 
import {userStore} from './someUserStoreModule';

// use 
import {getUserstore} from './someUserStoreModule';
const userStore = getUserstore();