Firebase React Native -- how to grab and transmit Device ID/Token?

Question

First time Firebase and RN user here, trying to figure out how to transmit the Device ID/Token of the app user.

I'm using something basic like this to transmit information to my firebase database right now (using firebase.database().ref()).

  updateDB = (timestamp_key, item_name, item_url) => {
    firebase.database().ref(timestamp_key).set({
      item_name: item_name,
      item_url: item_url
    })
  }

I haven't been able to find a simple straightforward answer as to how to fetch one's device token and transmit that as well (so I know whose action is whose later).

Is there a (what I think should be) a relatively straightforward way to do that? Thanks!

P.S. I am calling this higher up in the script in addition to the configs to initialize the connection -- maybe it's somewhere around here I need to grab the device token?

// Initialize Firebase
const firebaseConfig = {
  apiKey: "blah",
  authDomain: "blah",
  databaseURL: "blah",
  storageBucket: "blah",
  messagingSenderId: "blah"
};

firebase.initializeApp(firebaseConfig);

Answer 1

So I'm using Expo with React Native as well. However, I'm using Google's Cloud Firestore instead of realtime database.

I'm not sure I understand your question completely, but this is how I am doing it:

const firebase = require('firebase');
import { Constants } from 'expo';

// Required for side-effects
require('firebase/firestore');
import { firebaseConfig } from './../keys';

class Fire {
  constructor() {
    this.init();
    this.observeAuth();
  }

  init = () => firebase.initializeApp(firebaseConfig);

  observeAuth = () => firebase.auth().onAuthStateChanged(this.onAuthStateChanged);

  onAuthStateChanged = user => {
    if (!user) {
      try {
        firebase.auth().signInAnonymously();
      } catch ({ message }) {
        console.warn(message);
      }
    } else {
      this.saveUser();
    }
  };

  saveUserInfo = () => {
    const { uid } = this;
    if (!uid) {
      return;
    }
    // You can add any information here
    const info = {
      deviceId: Constants.deviceId,
    };
    const ref = this.db.collection('users').doc(uid);
    const setWithMerge = ref.set({ uid, ...info }, { merge: true });
  };

  get db() {
    return firebase.firestore();
  }
  get uid() {
    return (firebase.auth().currentUser || {}).uid;
  }
}

Fire.shared = new Fire();
export default Fire;

I got most of this code from Evan Bacon's example - https://github.com/EvanBacon/Expo-Pillar-Valley.