This document discusses Firebase, a cloud-based NoSQL database service founded in 2011 and acquired by Google in 2014. It highlights key features such as real-time data synchronization, offline capabilities, and various authentication methods, along with tips on using Firebase in mobile app development. The presentation also critiques potential downsides, such as limited visibility during failures and the necessity of correct data structuring.

1. Firebase: Totally Not
Parse All Over Again
(Unless It Is)
Chris Adamson (@invalidname)
CocoaConf DC • September, 2016
Slides will be available at slideshare.net/invalidname
Code will be available at github.com/invalidstream

3. 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

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

5. 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)

6. 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

7. Getting Started
• Create app on firebase.google.com using your
apps bundle identifier
• Download and add GoogleService-info.plist to
your project

10. 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

11. 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
}

12. Demo

13. 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

14. Tree-structured data

15. 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.

16. 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")

17. Now What?

18. 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

19. 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()
})

20. Parse!
• Observer block receives a FIRDataSnapshot for
every change
• Immutable, fetch contents with .value()
• Value types: NSDictionary, NSArray (rare),
NSString, NSNumber [or Swift equivalents]

21. Parse sessions list
private 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)
}
}
}

22. Parse a session
init? (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)

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

24. Demo: Writing data back to
Firebase

25. Creating a location
if 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()
}

26. childByAutoId()

27. Setting a value
let firebaseUserFavorites = firebaseUser?.child("favorites")
let firebaseFavorite = firebaseUserFavorites?.child(sessionId)
firebaseFavorite?.setValue(true)

28. Lists of stuff
• Convention is to have a dict where keys are ids
and values are just “true”

29. 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

30. 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

31. 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

32. 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

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

34. 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

35. 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"
}
}
}
}

36. Case Study

37. 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

38. MathElf Demo

39. 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

40. User Metadata

41. Page Contents

42. Picture metadata

43. Drawing paths

44. mathelf.com

45. 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

46. 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.

47. Firebase: Totally Not
Parse All Over Again
(Unless It Is)
Chris Adamson (@invalidname)
CocoaConf DC • September, 2016
Slides will be available at slideshare.net/invalidname
Code will be available at github.com/invalidstream