Firebase: Totally Not Parse All Over Again

(Unless It Is)Chris Adamson (@invalidname)

CocoaConf San Jose • November, 2016

Slides available at slideshare.net/invalidname Code available at github.com/invalidstream

Firebase

• Founded in 2011

• Offshoot of Envolve, a chat service that game developers started using to sync state across devices

• Main product is a realtime database

• Acquired by Google in October 2014

https://techcrunch.com/2016/05/18/google-turns-firebase-into-its-unified-platform-for-mobile-developers/

Firebase @ Google

• 470,000 developers using Firebase

• Arguably the star of Google I/O 2016

• Analytics (from developers of Google Analytics)

• Notifications (based on Google Cloud Messaging)

Realtime database

• Cloud-based NoSQL database

• Syncs instantly across devices, handles going offline

• Client SDKs for iOS and Android, REST for web

• Free tier supports 100 simultaneous users, 1GB storage

Getting Started

• Create app on firebase.google.com using your apps bundle identifier

• Download and add GoogleService-info.plist to your project

Getting Started

• Add the Firebase Cocoapod

• As with all things pod, remember to use .xcworkspace instead of .xcproj from now on

• Yes, it is possible to add the frameworks without Cocoapods

Getting Started

• Initialize Firebase in application(_: didFinishLaunchingWithOptions:)

import Firebase

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool { // Override point for customization after application launch. FIRApp.configure() return true }

Demo

Wait, what the…

• Firebase I/O works with a local cache, which in turn syncs with the backend

• With good connectivity, syncing to backend and other devices is instantaneous

• When offline, you can keep working with your local db, which syncs when you’re back online

Tree-structured data

Tree-structured data• Your database is basically one big JSON tree

• You access branches and nodes by path

• e.g., /sessions/adamson-firebase/title

• You can query at a given location, but this is not a relational database.

• If you want to do a table join, you structured your data incorrectly. Prefer flatness.

Getting a Firebase Reference

• FIRDatabase.reference() returns root of tree as a FIRDatabaseReference

• Child returns the named child as a FIRDatabaseReference

firebaseSessions = FIRDatabase.database().reference(). child("sessions")

Now What?

Observing Firebase

• All interactions with Firebase are asynchronous

• You don’t read the value of a location, you observe it for changes

• Contents of the child are passed to you on every change

Observe!

• eventType: the type of event you want to observe (value, child CRUD, etc)

• block: a closure to execute on these events

• returns a handle (dispose it in deinit, or earlier)

firebaseHandle = firebaseSessions?.observe( FIRDataEventType.value, with: { [weak self] (snapshot) in self?.parseSessionsFrom(snapshot) self?.tableView.reloadData() })

Parse!

• Observer block receives a FIRDataSnapshot for every change

• Immutable, fetch contents with .value()

• Value types: NSDictionary, NSArray (rare), NSString, NSNumber [or Swift equivalents]

Parse sessions listprivate func parseSessionsFrom(_ snapshot: FIRDataSnapshot) { guard let fbSessions = snapshot.value as? [String : Any] else { return } sessions.removeAll() for (id, value) in fbSessions { if let sessionDict = value as? [String : Any], let session = Session(id: id, dict: sessionDict) { sessions.append(session) } } }

Parse a sessioninit? (id: String, dict : [String : Any]) { guard let title = dict["title"] as? String, let speakerName = dict["speakerName"] as? String, let description = dict["description"] as? String else { return nil } self.id = id self.title = title self.speakerName = speakerName self.description = description }

Note: id is the node name (the key in the dictionary on the last slide)

Tip!

• FIRDatabaseReference.url can be pasted into your browser to view the Firebase console for that location in your db.

Demo: Writing data back to Firebase

Creating a locationif let oldId = UserDefaults.standard.string(forKey: "userId") { firebaseUser = firebaseAttendees?.child(oldId) } else { firebaseUser = firebaseAttendees?.childByAutoId() let newId = firebaseUser?.key let firebaseUserName = firebaseUser?.child("name") firebaseUserName?.setValue("Foo Bar") UserDefaults.standard.setValue(newId, forKey: "userId") UserDefaults.standard.synchronize() }

childByAutoId()

Setting a value

let firebaseUserFavorites = firebaseUser?.child("favorites") let firebaseFavorite = firebaseUserFavorites?.child(sessionId) firebaseFavorite?.setValue(true)

Lists of stuff• Convention is to have a dict where keys are ids

and values are just “true”

Arrays in Firebase ಠ_ಠ

• A dictionary with numeric keys in order will be sent to your observer as an array rather than a dictionary

• Not as convenient as you’d think. Pretty much a Firebase anti-pattern

observeSingleEvent()favoriteTitles.removeAll() for (sessionId, _) in fbFavorites { firebaseSessions?.child(sessionId).child(“title").observeSingleEvent( of: FIRDataEventType.value, with: { [weak self] snapshot in if let title = snapshot.value as? String { self?.favoriteTitles.append( FavoriteItem(favoriteId: sessionId, title: title)) self?.tableView.reloadData() } }) }

Note: observeSingleEvent() does not return a handle for you to hold on to and dispose later

Authentication• Firebase provides an email + password system

• Can also use Google, Twitter, Facebook, or GitHub credentials

• Or roll your own and provide an OAuth token

Database rules

• Define per-branch access based on authentication

• Can require that user just be logged in, or that their Firebase user id matches the one that created the node

Default access

// These rules require authentication{  "rules": {    ".read": "auth != null",    ".write": "auth != null"  }}

Public access

// These rules give anyone, even people who are not users of your app,// read and write access to your database{  "rules": {    ".read": true,    ".write": true  }}

Private access: just make read/write false

User access// These rules grant access to a node matching the authenticated// user's ID from the Firebase auth token{  "rules": {    "users": {      "$uid": {        ".read": "$uid === auth.uid",        ".write": "$uid === auth.uid"      }    }  }}

Case Study

MathElf

• “Über for high-school math tutoring”

• Students request help on a topic, are paired with a tutor in less than a minute

• Student and tutor work on problems via voice chat and a shared whiteboard

MathElf Demo

MathElf & Firebase

• Authentication and user financials are done through rev.com (parent company) backend, making REST calls to Firebase

• Basically everything in the whiteboard and session history is Firebase

User Metadata

Page Contents

Picture metadata

Drawing paths

mathelf.com

Firebase “con”s

• Limited visibility when something goes wrong

• When things don’t sync, is it them or you?

• Single point of failure, owned and operated by a third party

• Could be Parse all over again

Takeaways• Firebase database-as-a-service is well-suited to

mobile apps

• Real-time sync, still works when offline

• Structure your data as flat JSON trees, not SQL-like tables

• All reads are asynchronous. Hope you like closures/blocks.

Firebase: Totally Not Parse All Over Again

(Unless It Is)Chris Adamson (@invalidname)

CocoaConf San Jose • November, 2016

Slides available at slideshare.net/invalidname Code available at github.com/invalidstream