🌐 📍 Geolocation Queries with Firestore & RxJS
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README.md

GeoFireX

Realtime Geolocation with Firestore & RxJS

👉 Live Demo 📺 Video Tutorial

🏁 QuickStart

npm install geofirex

# peer dependencies
npm install rxjs firebase

Initialize

The library is a lightweight client for the Firebase Web SDK that provides tools for wrangling geolocation data in Firestore. You need a Firebase project to get started.

// Init Firebase
import * as firebase from 'firebase/app';
firebase.initializeApp(yourConfig);

// Init GeoFireX
import * as geofirex from 'geofirex';
const geo = geofirex.init(firebase);

Write Geo Data

Next, add some geolocation data in your database. A collection creates a reference to Firestore (just like the SDK), but with some extra geolocation tools. The point method returns a class that helps you create geolocation data.

const cities = geo.collection('cities');

const point = geo.point(40, -119);

cities.add({ name: 'Phoenix', position: point.data });

Calling point.data returns an object that contains a geohash string and a Firestore GeoPoint. It should look like this in your database. You can name the object whatever you want and even save multiple points on a single document.

Query Geo Data

Now let's query Firestore for cities.position within 100km radius of a centerpoint.

const center = geo.point(40.1, -119.1);
const radius = 100;
const field = 'position';

const query = cities.within(center, radius, field);

The query returns a realtime Observable of the document data, plus some useful metadata like distance and bearing from the query centerpoint.

query.subscribe(console.log);
// [{ ...documentData, queryMetadata: { distance: 1.23232, bearing: 230.23 }  }]

You now have a realtime stream of data to visualize on a map.

📓 API

collection(path: string, query? QueryFn)

Creates reference to a Firestore collection that can be used to make geo-queries and perform writes If you pass an optional Firestore query function, all subsequent geo-queries will be limited to this subset of documents

Example:

const collection = geo.collection('cities');

Performing Geo-Queries

collection.within(center: GeoFirePoint, radius: number, field: string)

Query the parent Firestore collection by geographic distance. It will return documents that exist within X kilometers of the centerpoint.

Each doc also contains returns distance and bearing calculated on the query on the queryMetadata property.

Returns: Observable<object[]>

Write Data

Write data just like you would in Firestore

collection.add(data)

Or use one of the client's conveniece methods

  • collection.setDoc(id, data) - Set a document in the collection with an ID.
  • collection.setPoint(id, field, lat, lng)- Add a geohash to an existing doc

Read Data

In addition to Geo-Queries, you can also read the collection like you would normally in Firestore, but as an Observable

  • collection.data()- Observable of document data
  • collection.snapshot()- Observable of Firestore QuerySnapshot

point(latitude: number, longitude: number)

Returns a GeoFirePoint allowing you to create geohashes, format data, and calculate relative distance/bearing.

Example: const point = geo.point(38, -119)

Getters

  • point.hash Returns a geohash string at precision 9
  • point.geoPoint Returns a Firestore GeoPoint
  • point.geoJSON Returns data as a GeoJSON Feature<Point>
  • point.coords Returns coordinates as [latitude, longitude]
  • point.data Returns data object suitable for saving to the Firestore database

Geo Calculations

  • point.distance(latitude, longitude) Haversine distance to a point
  • point.bearing(latitude, longitude) Haversine bearing to a point

🍕 Additional Features

The goal of this package is to facilitate rapid feature development with tools like MapBox, Google Maps, and D3.js. If you have an idea for a useful feature, open an issue.

toGeoJSON Operator

A custom RxJS operator that transforms a collection into a GeoJSON FeatureCollection. Very useful for tools like MapBox that can use GeoJSON to update a realtime data source.

const query = geo.collection('cars').within(...)

query.pipe( toGeoJSON() )

// Emits a single object typed as a FeatureCollection<Geometry>
{
  "type": "FeatureCollection",
  "features": [...]
}

Promises with get

Don't need a realtime stream? Convert any query observable to a promise by wrapping it with get.

import { get } from 'geofirex';

async function getCars {
    const query = geo.collection('cars').within(...)
    const cars = await get(query)
}

⚡️ Tips

Scale to Massive Collections

It's possibe to build Firestore collections with billions of documents. One of the main motivations of this project was to make geoqueries possible on a queried subset of data. You can make a regular Firestore query on collection by passing a callback as the second argument, then all geoqueries will scoped these contstraints.

Note: This query requires a composite index, which you will be prompted to create with an error from Firestore on the first request.

Example:

const users = geo.collection('users', ref =>
  ref.where('status', '==', 'online')
);

const nearbyOnlineUsers = users.within(center, radius, field);

Usage with RxJS < 6.2, or Ionic v3

This package requires RxJS 6.2, but you can still use it with older versions without blowing up you app by installing rxjs-compat.

Example:

npm i rxjs@latest rxjs-compat

Seeing this error: DocumentReference.set() called with invalid data

Firestore writes cannot use custom classes, so make sure to call the data getter on the point.

const point = geo.point(40, -50);
// This is an ERROR
ref.add({ location: point });

// This is GOOD
ref.add({ location: point.data });

Make Dynamic Queries the RxJS Way

const radius = new BehaviorSubject(1);
const cities = geo.collection('cities');

const points = this.radius.pipe(
  switchMap(rad => {
    return cities.within(center, rad, 'point');
  })
);

// Now update your query
radius.next(23);

Always Order by [Latitude, Longitude]

The GeoJSON spec formats coords as [Longitude, Latitude] to represent an X/Y plane. However, the Firebase GeoPoint uses [Latitude, Longitude]. For consistency, this libary will always require you to use the latter format.