In this talk, I am going to walk you through the building blocks for creating modern applications on Apple’s platforms using SwiftUI and Firebase. We will cover the following topics: - Setting up an architecture for data-driven applications - What’s new in SwiftUI’s application life cycle - Syncing data in realtime across multiple devices with Cloud Firestore - Mapping Firestore documents in a type-safe way using the Codable protocol - Using Combine to fetch data from remote APIs and Firebase - How async/await (new in Swift 5.5) will affect the way we write asynchronous code (plus some surprises in Firebase's code base) Firebase is always evolving, so I will also talk about how we’re making use of Apple’s latest technologies in our own code base, for example - Combine - async/await - SwiftUI view modifiers No matter if you’re a seasoned Firebase user or just wondering what it is all about, you should leave this session with a deeper understanding of what Firebase it and how you can use it your apps on Apple’s platforms.

1. Peter Friese | Firebase Developer Advocate | @pete!riese
 +
Firebase for Apple Developers

2. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

3. Architecture
For Data-Driven Apps
Photo by Lance Anderson on Unsplash

4. #one-book-a-week-challenge

6. Drill-down navigation
Three-column layout (iPad / Mac)
Single source of truth
Driving factors
UI always in sync

7. UI always in sync

8. BookShelfView
BookEditView
BookDetailsView
BookRowView
Source of Truth
books: [Book]
@ObservableObject
@Binding
Book
Book
Book

9. Challenge 1
Sequences are not bindable!

10. struct BookShelfView: View {
@Binding var bookShelf: BookShelf
var body: some View {
List {
ForEach(Array(bookShelf.books.enumerated()), id: .element.id) { index, item in
BookRowView(book: $bookShelf.books[index])
}
.onDelete { indexSet in
bookShelf.books.remove(atOffsets: indexSet)
}
}
.navigationTitle(bookShelf.title)
}
}
Solution 1: iterate over enumerated items

11. struct BookShelfView: View {
@Binding var bookShelf: BookShelf
var body: some View {
List {
ForEach(Array(bookShelf.books.enumerated()), id: .element.id) { index, item in
BookRowView(book: $bookShelf.books[index])
}
.onDelete { indexSet in
bookShelf.books.remove(atOffsets: indexSet)
}
}
.navigationTitle(bookShelf.title)
}
}
Solution 1: iterate over enumerated items

12. Challenge 2
How to update only
when the user commits?

13. struct BookEditView: View {
@Binding var book: Book
@ObservedObject var bookEditViewModel: BookEditViewModel
init(book: Binding<Book>) {
self._book = book
self.bookEditViewModel = BookEditViewModel(book: book.wrappedValue)
}
var body: some View {
TextField("Book title", text: $bookEditViewModel.book.title)
}
func save() {
self.book = bookEditViewModel.book
presentationMode.wrappedValue.dismiss()
}
}
Solution 2: use inner @ObserverableObject

14. struct BookEditView: View {
@Binding var book: Book
@ObservedObject var bookEditViewModel: BookEditViewModel
init(book: Binding<Book>) {
self._book = book
self.bookEditViewModel = BookEditViewModel(book: book.wrappedValue)
}
var body: some View {
TextField("Book title", text: $bookEditViewModel.book.title)
}
func save() {
self.book = bookEditViewModel.book
presentationMode.wrappedValue.dismiss()
}
}
Solution 2: use inner @ObserverableObject

15. struct BookEditView: View {
@Binding var book: Book
@ObservedObject var bookEditViewModel: BookEditViewModel
init(book: Binding<Book>) {
self._book = book
self.bookEditViewModel = BookEditViewModel(book: book.wrappedValue)
}
var body: some View {
TextField("Book title", text: $bookEditViewModel.book.title)
}
func save() {
self.book = bookEditViewModel.book
presentationMode.wrappedValue.dismiss()
}
}
Solution 2: use inner @ObserverableObject

16. struct BookEditView: View {
@Binding var book: Book
@ObservedObject var bookEditViewModel: BookEditViewModel
init(book: Binding<Book>) {
self._book = book
self.bookEditViewModel = BookEditViewModel(book: book.wrappedValue)
}
var body: some View {
TextField("Book title", text: $bookEditViewModel.book.title)
}
func save() {
self.book = bookEditViewModel.book
presentationMode.wrappedValue.dismiss()
}
}
Solution 2: use inner @ObserverableObject

17. Solution 2

18. class BookEditViewModel: ObservableObject {
@Published var book: Book
@Published var isISBNValid: Bool = true
init(book: Book) {
self.book = book
self.$book
.map { checkISBN(isbn: $0.isbn) }
.assign(to: &$isISBNValid)
}
}
Solution 2: use inner @ObserverableObject
Bonus: use Combine to
perform validation

19. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

21. Run with confidence Engage users
Develop apps faster

22. Run with confidence
Crashlytics
Performance
Monitoring
Test Lab
App Distribution
Engage users
Analytics
Predictions
Cloud
Messaging
Remote
Config
A/B Testing
Dynamic
Links
In-app
Messaging
Develop apps faster
Auth
Cloud
Functions
Cloud
Firestore
Hosting
ML Kit
Realtime
Database
Cloud
Storage
bit.ly/what-is-firebase
Extensions
Machine
Learning

26. #protip: Put it
beneath Asset.xcasset

27. Don’t forget to add
to all the targets!

28. Swift Package Manager
now officially supported!
h"ps://github.com/#rebase/#rebase-ios-sdk

29. !

30. Application Lifecycle
SwiftUI 2
Photo by Thor Alvis on Unsplash

31. SwiftUI 2: No more AppDelegate!
import SwiftUI
@main
struct BookShelfApp: App {
@StateObject var store = BookShelfStore(shelves: BookShelf.samples)
var body: some Scene {
WindowGroup {
NavigationView {
BookShelvesView(store: store)
Text("Select a shelf to see its books")
Text("Select a book to see its details")
}
}
}
}

32. SwiftUI 2: No more AppDelegate!
import SwiftUI
@main
struct BookShelfApp: App {
@StateObject var store = BookShelfStore(shelves: BookShelf.samples)
var body: some Scene {
WindowGroup {
NavigationView {
BookShelvesView(store: store)
Text("Select a shelf to see its books")
Text("Select a book to see its details")
}
}
}
}

33. Solution 1: use initialiser
import SwiftUI
@main
struct BookShelfApp: App {
@StateObject var store = BookShelfStore(shelves: BookShelf.samples)
var body: some Scene {
WindowGroup {
NavigationView {
BookShelvesView(store: store)
Text("Select a shelf to see its books")
Text("Select a book to see its details")
}

34. Solution 1: use initialiser
import SwiftUI
@main
struct BookShelfApp: App {
@StateObject var store = BookShelfStore(shelves: BookShelf.samples)
var body: some Scene {
WindowGroup {
NavigationView {
BookShelvesView(store: store)
Text("Select a shelf to see its books")
Text("Select a book to see its details")
}
init() {
FirebaseApp.configure()
}

35. Solution 2: use UIApplicationDelegateAdaptor
import SwiftUI
import Firebase
class AppDelegate: NSObject, UIApplicationDelegate {
func application(_ application: UIApplication,
didFinishLaunchingWithOptions
launchOptions:
[UIApplication.LaunchOptionsKey : Any]? = nil) !" Bool {
FirebaseApp.configure()
return true
}
}
@main
struct BookShelfApp: App {
@UIApplicationDelegateAdaptor(AppDelegate.self) var delegate

36. Solution 2: use UIApplicationDelegateAdaptor
import SwiftUI
import Firebase
class AppDelegate: NSObject, UIApplicationDelegate {
func application(_ application: UIApplication,
didFinishLaunchingWithOptions
launchOptions:
[UIApplication.LaunchOptionsKey : Any]? = nil) !" Bool {
FirebaseApp.configure()
return true
}
}
@main
struct BookShelfApp: App {
@UIApplicationDelegateAdaptor(AppDelegate.self) var delegate

37. Solution 2: use UIApplicationDelegateAdaptor
import SwiftUI
import Firebase
class AppDelegate: NSObject, UIApplicationDelegate {
func application(_ application: UIApplication,
didFinishLaunchingWithOptions
launchOptions:
[UIApplication.LaunchOptionsKey : Any]? = nil) !" Bool {
FirebaseApp.configure()
return true
}
}
@main
struct BookShelfApp: App {
@UIApplicationDelegateAdaptor(AppDelegate.self) var delegate

38. Solution 2: use UIApplicationDelegateAdaptor
import SwiftUI
import Firebase
class AppDelegate: NSObject, UIApplicationDelegate {
func application(_ application: UIApplication,
didFinishLaunchingWithOptions
launchOptions:
[UIApplication.LaunchOptionsKey : Any]? = nil) !" Bool {
FirebaseApp.configure()
return true
}
}
@main
struct BookShelfApp: App {
@UIApplicationDelegateAdaptor(AppDelegate.self) var delegate

39. Watch the scene phase
Handle deep links
Continue user activities
Do more with the new life cycle

40. Watch the scene phase
Handle deep links
Continue user activities
Learn more
pete$riese.dev/ultimate-guide-to-swi!ui2-application-lifecycle/

41. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

42. Firestore

45. One-Time Fetches
Offline Mode
Effortless Syncing

46. bird_type:
airspeed:
coconut_capacity:
isNative:
icon:
vector:
distances_traveled:
"swallow"
42.733
0.62
false
<binary data>
{x: 36.4255,
y: 25.1442,
z: 18.8816}
[42, 39, 12, 42]
Document

47. Collection
Sub-Collection

48. Top level
collections
“books” collection a single book document

49. struct Book: Identifiable {
var id = UUID().uuidString
var shelfId: String?
var userId: String?
var title: String
var author: String
var isbn: String
var pages: Int
var isRead: Bool = false
var coverEditionKey: String?
}
Data Model

50. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

51. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

52. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

53. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

54. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

55. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

56. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore
Can we do better?

57. (Yes, we can)

58. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Fetching a document from Firestore

59. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Mapping data using Codable
if let document = document {
do {
self.book = try document.data(as: Book.self)
}
catch {
print(error)
}
}

60. func fetchBook(documentId: String) {
let docRef = Firestore.firestore().collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
print("Error getting document: (error.localizedDescription)")
} else {
if let document = document {
let id = document.documentID
let data = document.data()
let title = data?["title"] as? String !# ""
let numberOfPages = data?["numberOfPages"] as? Int !# 0
let author = data?["author"] as? String !# ""
self.book = Book(id:id, title: title,
numberOfPages: numberOfPages, author: author)
}
}
}
}
Mapping data using Codable
if let document = document {
do {
self.book = try document.data(as: Book.self)
}
catch {
print(error)
}
}

61. BookShelfView
BookEditView
BookDetailsView
BookRowView
Source of Truth
books: [Book]
@ObservableObject
@Binding
Book
Book
Book
Review: Architecture

62. BookShelfView
BookDetailsView
BookRowView
Source of Truth
books: [Book]
@ObservableObject
@Binding
Book
Book
Review: Architecture
Snapshot Listener

63. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

64. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

65. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

66. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

67. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

68. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

69. class BookStore: ObservableObject {
var db = Firestore.firestore()
private var listenerRegistration: ListenerRegistration?
@Published var books = [Book]()
func subscribe() {
listenerRegistration = db.collection("books")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot!$documents else { return }
self!$books = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: Book.self) }
switch result {
case .success(let book):
if let book = book {
return book
Fetching a collection of documents

71. Learn more
h"ps://pete$riese.dev/#restore-codable-the-comprehensive-guide/

72. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

73. Authentication
Photo by Conve"Kit on Unsplash

74. Authentication
Photo by Eduardo Soares on Unsplash

75. Authentication
Photo by Victor Freitas on Unsplash

76. 

77. Sign in the user
Update the data model
Secure users’ data
How to implement
Firebase Authentication?

78. Anonymous Authentication
“Guest” accounts, rather

79. func signIn() {
registerStateListener()
if Auth.auth().currentUser !% nil {
Auth.auth().signInAnonymously()
}
}
Anonymous Authentication

81. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

82. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

83. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

84. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

85. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

86. SignInWithAppleButton(
onRequest: { !!& },
onCompletion: { result in
!!&
let appleIDToken = appleIDCredential.identityToken
let idTokenString = String(data: appleIDToken, encoding: .utf8)
let credential = OAuthProvider.credential(withProviderID: “apple.com",
idToken: idTokenString,
rawNonce: nonce)
Auth.auth().signIn(with: credential) { (authResult, error) in
if (error !' nil) { !!& }
self.presentationMode.wrappedValue.dismiss()
}
}
).frame(width: 280, height: 45, alignment: .center)
Sign in with Apple

87. All books are stored in one single collection
Which user do
they belong to?

88. let query = db.collection("books")
.whereField("userId",
isEqualTo: self.userId)
query
.addSnapshotListener { [weak self] (querySnapsho
guard let documents = querySnapshot!$documents els
Signed in user

89. rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
match /{document=**} {
allow create: if request.auth !' null;
allow read, update, delete: if request.auth !' null
!( resource.data.userId !% request.auth.uid;
}
}
}
Security Rules
Only signed-in users can
create new documents
Only owners may read and
modify a document

90. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

91. Combine

92. auth!$signInAnonymously()
let user = auth!$currentUser
print("User signed in with user ID: (user!$uid)")
This might be nil

93. auth!$signInAnonymously()
let user = auth!$currentUser
print("User signed in with user ID: (user!$uid)")
auth!$signInAnonymously { result, error in
guard let result = result else {
return
}
print("User signed in with user ID: (result.user.uid)")
}
Do this instead

94. auth!$signInAnonymously()
let user = auth!$currentUser
print("User signed in with user ID: (user!$uid)")
auth!$signInAnonymously { result, error in
guard let result = result else {
return
}
print("User signed in with user ID: (result.user.uid)")
}
@Published var user: User?
!!&
auth!$signInAnonymously()
.map{ $0.user }
.replaceError(with: nil)
.assign(to: &$user)
Even better

95. Follow the project for updates
h"ps://github.com/#rebase/#rebase-ios-sdk/projects/3

96. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

97. async/await
Photo by Stephen H on Unsplash

98. extension ArticleAnalyser {
func process(url: String, completion: @escaping (Article) !" Void) {
self.fetchArticle(from: url) { result in
switch result {
case .failure(let error):
print(error.localizedDescription)
case .success(let html):
self.extractTitle(from: html) { result in
switch result {
case .failure(let error):
print(error.localizedDescription)
case .success(let title):
self.extractText(from: html) { result in
switch result {
case .failure(let error):
print(error.localizedDescription)
case .success(let text):
self.extractImage(from: url) { result in
Problem: Callback Pyramid of Doom

99. extension AsyncArticleAnalyser {
func process(url: String) async throws !" Article {
let htmlText = try await fetchArticle(from: url)
let text = try await extractText(from: htmlText)
let title = try await extractTitle(from: htmlText)
let imageUrl = try await extractImage(from: url)
let tags = await inferTags(from: text)
return Article(url: url,
title: title,
tags: tags,
imageUrlString: imageUrl)
}
}
Solution: Use async/await
Probably in Swift 5.5

100. func fetchArticle(from url: String) async throws !" String {
guard let url = URL(string: url) else { throw AnalyserError.badURL }
return try await withUnsafeThrowingContinuation { continuation in
URLSession.shared.downloadTask(with: url) { (localUrl, urlResponse, error) in
guard let localUrl = localUrl else {
continuation.resume(throwing: AnalyserError.badURL)
return
}
if let htmlText = try? String(contentsOf: localUrl) {
continuation.resume(returning: htmlText)
}
}
.resume()
}
}
Solution: Use async/await
Probably in Swift 5.5

101. func fetchArticle(from url: String) async throws !" String {
guard let url = URL(string: url) else { throw AnalyserError.badURL }
return try await withUnsafeThrowingContinuation { continuation in
URLSession.shared.downloadTask(with: url) { (localUrl, urlResponse, error) in
guard let localUrl = localUrl else {
continuation.resume(throwing: AnalyserError.badURL)
return
}
if let htmlText = try? String(contentsOf: localUrl) {
continuation.resume(returning: htmlText)
}
}
.resume()
}
}
Solution: Use async/await
Probably in Swift 5.5

102. func fetchArticle(from url: String) async throws !" String {
guard let url = URL(string: url) else { throw AnalyserError.badURL }
return try await withUnsafeThrowingContinuation { continuation in
URLSession.shared.downloadTask(with: url) { (localUrl, urlResponse, error) in
guard let localUrl = localUrl else {
continuation.resume(throwing: AnalyserError.badURL)
return
}
if let htmlText = try? String(contentsOf: localUrl) {
continuation.resume(returning: htmlText)
}
}
.resume()
}
}
Solution: Use async/await
Probably in Swift 5.5

103. func fetchArticle(from url: String) async throws !" String {
guard let url = URL(string: url) else { throw AnalyserError.badURL }
return try await withUnsafeThrowingContinuation { continuation in
URLSession.shared.downloadTask(with: url) { (localUrl, urlResponse, error) in
guard let localUrl = localUrl else {
continuation.resume(throwing: AnalyserError.badURL)
return
}
if let htmlText = try? String(contentsOf: localUrl) {
continuation.resume(returning: htmlText)
}
}
.resume()
}
}
Solution: Use async/await
Probably in Swift 5.5

104. auth!$signInAnonymously { result, error in
guard let result = result else {
return
}
print("User signed in with user ID: (result.user.uid)")
}
do {
let result = try await Auth.auth().signIn(withEmail: email, password: password)
print("User signed in with user ID: (result.user.uid)")
}
catch {
print(error)
}
Works with Firebase, too!
Callback-style

105. Learn more
h"ps://pete$riese.dev/async-await-in-swi!
h"ps://www.youtube.com/watch?v=sEKw2BMcQtQ

106. Architecture Swi!UI 2 Life Cycle
Firebase Firestore Authentication Combine async/await Completion block

107. Thanks!
Peter Friese
h"p://pete$riese.dev
@pete$riese
youtube.com/c/PeterFriese/
Follow me

108. Credits
#nish by Megan Chown from the Noun Project
Time by Nikita Kozin from the Noun Project
pipe by Komkrit Noenpoempisut from the Noun Project
Passpo% by ProSymbols from the Noun Project
spiral by Alexander Skowalsky from the Noun Project
Architecture by Ervin Bolat from the Noun Project
Firebase logos cou%esy h"ps://#rebase.google.com/brand-guidelines
Firebase logos cou%esy h"ps://#rebase.google.com/brand-guidelines
Thanks!
Hea% by Roman from the Noun Project

109. The End.