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Replace API to Firebase Database
- The view from client side
Daiki Matsudate / @d_date
2017/11/03 / Serverlessconf Tokyo 2017
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Daiki Matsudate
iOS Mobile App Engineer
@d_date
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Tokyo
2018/3/1 - 3
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Firebase
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Firebase
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Cloud Messaging
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31 Oct. at Amsterdam
#FirebaseSummit
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• Prediction
• A/B Testing
• Integrate Crashlytics into Firebase
#FirebaseSummit
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#FirebaseSummit
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Agenda
• Firebase Realtime Database
• Feature
• Introduce to Mobile App
• Architecture
• Testing
• ???
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Firebase Database
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• NoSQL cloud database
• Realtime Data Sync with JSON Tree
• Available data on offline
Firebase Database
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Firebase Database
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Replace API to Realtime Database
Case Study
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Replace API to Realtime Database
API
Client (Native App) Server
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Client (Native App) Server
Firebase
Database
Replace API to Realtime Database
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Replace API to Realtime Database
• use func observeSingleEvent(:_) in FirebaseDatabase
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Replace API to Realtime Database
• Reduce building API man-hours
• No more performance tunings
• Easy to handle data in offline
Purpose
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Client (Native App) Server
Firebase
Database
Replace API to Realtime Database
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Client (Native App)
Firebase
Database
Replace API to Realtime Database
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NoSQL
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NoSQL = Denormalization
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Denormalization in NoSQL
{
"users": {
"user1": {
"name": "Alice"
},
"user2": {
"name": "Bob"
}
},
"links": {
"link1": {
"title": "Example",
"href": "http://example.org",
"submitted": "user1"
}
},
"comments": {
"comment1": {
"link": "link1",
"body": "This is awesome!",
"author": "user2"
}
}
}
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Denormalization in NoSQL
{
"users": {
"user1": {
"name": "Alice"
},
"user2": {
"name": "Bob"
}
},
"links": {
"link1": {
"title": "Example",
"href": "http://example.org",
"submitted": "user1"
}
},
"comments": {
"comment1": {
"link": "link1",
"body": "This is awesome!",
"author": "user2"
}
}
}
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Denormalization in NoSQL
{
"users": {
"user1": {
"name": "Alice"
},
"user2": {
"name": "Bob"
}
},
"links": {
"link1": {
"title": "Example",
"href": "http://example.org",
"submitted": "user1"
}
},
"comments": {
"comment1": {
"link": "link1",
"body": "This is awesome!",
"author": "user2"
}
}
}
Join data in client
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JOIN data in client in Swift
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
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Not Swifty!!
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
“Stringly“ typed
Pyramid of Death
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Easy to replace from API?
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
Need reference of database
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To make friend with NoSQL in Swift
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To make friend with NoSQL in Swift
• Re-Design Architecture
• Introduce Reactive Programming
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Re-Design Architecture
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!Architecture → Ideal State
"Ideal State → Architecture
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Ideal State
• Data from Firebase ≠ Data in app -> Need translation
• Easy to replace from API to Firebase
-> I/F is same as API, then want to replace DAO
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Replaceable Data Access Object
Entity
Data Access
to API
Data Access
Interface
(Repository)
Server
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Replaceable Data Access Object
Entity
Data Access
to Firebase
Data Access
Interface
(Repository)
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Translation
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
View
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Requirement for Architecture
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
View
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What is this architecture?
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
Presenter
View
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How to resolve Pyramid of Death
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
Pyramid of Death
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How to resolve Pyramid of Death
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
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protocol Entity: Codable {}
struct UserEntity: Entity {
let name: String
}
struct LinkEntity: Entity {
let title: String
let href: URL
let submitted: String
}
struct CommentEntity: Entity {
let link: String
let body: String
let author: String
}
Entity
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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Data Access + RxSwift
extension DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
self.observeSingleEvent(of: .value, with: { (snapshot) in
guard let jsonObject = snapshot.value else {
observer(.error(ProviderError.valueNotExist))
return
}
do {
let data = try JSONSerialization.data(withJSONObject: jsonObject)
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch(let error) {
observer(.error(error))
}
})
return Disposables.create()
})
}
}
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Data Access + RxSwift
extension DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
self.observeSingleEvent(of: .value, with: { (snapshot) in
guard let jsonObject = snapshot.value else {
observer(.error(ProviderError.valueNotExist))
return
}
do {
let data = try JSONSerialization.data(withJSONObject: jsonObject)
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch(let error) {
observer(.error(error))
}
})
return Disposables.create()
})
}
}
If value not exist,
invoke error
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Data Access + RxSwift
extension DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
self.observeSingleEvent(of: .value, with: { (snapshot) in
guard let jsonObject = snapshot.value else {
observer(.error(ProviderError.valueNotExist))
return
}
do {
let data = try JSONSerialization.data(withJSONObject: jsonObject)
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch(let error) {
observer(.error(error))
}
})
return Disposables.create()
})
}
}
If fail to serialize JSON,
invoke error
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Data Provider
class DataProvider {
static let shared = DataProvider()
private init() {}
lazy var ref: DatabaseReference = {
return Database.database().reference()
}()
func getUser(key: String) -> Single {
return ref.child("users").child(key).get()
}
func getLink(key: String) -> Single {
return ref.child("links").child(key).get()
}
func getComments() -> Single {
return ref.child("comments").get()
}
}
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Data Provider
class DataProvider {
static let shared = DataProvider()
private init() {}
lazy var ref: DatabaseReference = {
return Database.database().reference()
}()
func getUser(key: String) -> Single {
return ref.child("users").child(key).get()
}
func getLink(key: String) -> Single {
return ref.child("links").child(key).get()
}
func getComments() -> Single {
return ref.child("comments").get()
}
}
Singleton in Swift
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Data Provider
class DataProvider {
static let shared = DataProvider()
private init() {}
lazy var ref: DatabaseReference = {
return Database.database().reference()
}()
func getUser(key: String) -> Single {
return ref.child("users").child(key).get()
}
func getLink(key: String) -> Single {
return ref.child("links").child(key).get()
}
func getComments() -> Single {
return ref.child("comments").get()
}
}
Retain DatabaseReference
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Data Provider
class DataProvider {
static let shared = DataProvider()
private init() {}
lazy var ref: DatabaseReference = {
return Database.database().reference()
}()
func getUser(key: String) -> Single {
return ref.child("users").child(key).get()
}
func getLink(key: String) -> Single {
return ref.child("links").child(key).get()
}
func getComments() -> Single {
return ref.child("comments").get()
}
}
Get Entity from Database,
then return Single
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Data Access
struct UserRepository {
let dataStore: LinkDataStore
func get(userId: String) -> Single {
return dataStore.get(key: userId)
}
}
struct UserDataStore {
let provider = DataProvider.shared
func get(key: String) -> Single {
return provider.getUser(key: key)
}
}
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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Data Access
struct UserRepository {
let dataStore: LinkDataStore
func get(userId: String) -> Single {
return dataStore.get(key: userId)
}
}
struct UserDataStore {
let provider = DataProvider.shared
func get(key: String) -> Single {
return provider.getUser(key: key)
}
}
I/F for data access
Implementation for data
access
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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Interactor (UseCase)
struct UseCase {
let commentsRepository: CommentRepository
let usersRepository: UserRepository
let linksRepository: LinkRepository
func getComments() -> Single<[CommentModel]> {
return commentsRepository.get()
.map { (comment) -> [CommentModel] in
let link = self.getLink(linkId: comment.link)
let author = self.getUser(userId: comment.author)
return Single<(LinkModel, UserModel)>.zip(link, author) {
($0, $1)
}).map(translator: CommentTranslator())
}
}
}
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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Before
self.ref.child("comments").observeSingleEvent(of: .value, with: { [weak self] (snapshot) in
guard let strongSelf = self else { return }
guard let comments = snapshot.value as? [String: Any] else { return }
comments.forEach({ (key, value) in
guard let comment = value as? [String: Any] else { return }
let linkKey: String = comment["link"] as! String // "link1"
let authorKey: String = comment["author"] as! String // "user2"
strongSelf.ref.child("links").child(linkKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let link = snapshot.value as? [String: Any] else { return }
let submittedKey: String = link["submitted"] as! String // "user1"
strongSelf.ref.child("users").child(submittedKey).observeSingleEvent(of: .value, with:
{ (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Alice"
print(name)
})
})
strongSelf.ref.child("users").child(authorKey).observeSingleEvent(of: .value, with: { (snapshot) in
guard let user = snapshot.value as? [String: Any] else { return }
let name: String = user["name"] as! String // “Bob”
print(name)
})
})
})
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Presenter
class Presenter {
let useCase: UseCase
init(useCase: UseCase) {
self.useCase = useCase
}
func getComments() -> Single<[CommentModel]> {
return useCase.getComments()
}
}
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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View
class ViewController: UIViewController {
weak var presenter: Presenter!
private let disposeBag = DisposeBag()
func inject(presenter: Presenter) {
self.presenter = presenter
}
override func viewDidLoad() {
super.viewDidLoad()
presenter.getComments()
.subscribe(onSuccess: { (models) in
//Handling model
}, onError: { (error) in
//Handling Error
}).disposed(by: disposeBag)
}
}
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
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View
class ViewController: UIViewController {
weak var presenter: Presenter!
private let disposeBag = DisposeBag()
func inject(presenter: Presenter) {
self.presenter = presenter
}
override func viewDidLoad() {
super.viewDidLoad()
presenter.getComments()
.subscribe(onSuccess: { (models) in
//Handling model
}, onError: { (error) in
//Handling Error
}).disposed(by: disposeBag)
}
}
Entity
Data Access
Data
Access
Interactor
Model
Presenter
View
Focus on UI Handling
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Side Effect
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Side Effect
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
Presenter
View
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Side Effect - Easy Unit Testing
Entity
Data Access
Interface
Mock Object
Interactor
Model
Presenter
View
Easy to replace
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class DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
guard let bundlePath = Bundle(for: type(of: self)).path(forResource: "Stub", ofType: "bundle") else {
observer(.error(SerializeError.missingBundle))
return Disposables.create()
}
let jsonName = String(describing: T.self)
guard let path = Bundle(path: bundlePath)?.path(forResource: jsonName, ofType: "json") else {
observer(.error(SerializeError.missingJson(jsonName: jsonName)))
return Disposables.create()
}
do{
let data = try Data(contentsOf: URL(fileURLWithPath: path))
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch {
observer(.error(error))
}
return Disposables.create()
})
}
}
Side Effect - Easy Unit Testing
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class DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
guard let bundlePath = Bundle(for: type(of: self)).path(forResource: "Stub", ofType: "bundle") else {
observer(.error(SerializeError.missingBundle))
return Disposables.create()
}
let jsonName = String(describing: T.self)
guard let path = Bundle(path: bundlePath)?.path(forResource: jsonName, ofType: "json") else {
observer(.error(SerializeError.missingJson(jsonName: jsonName)))
return Disposables.create()
}
do{
let data = try Data(contentsOf: URL(fileURLWithPath: path))
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch {
observer(.error(error))
}
return Disposables.create()
})
}
}
Side Effect - Easy Unit Testing
FackObject
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class DatabaseReference {
func get() -> Single {
return Single.create(subscribe: { (observer) in
guard let bundlePath = Bundle(for: type(of: self)).path(forResource: "Stub", ofType: "bundle") else {
observer(.error(SerializeError.missingBundle))
return Disposables.create()
}
let jsonName = String(describing: T.self)
guard let path = Bundle(path: bundlePath)?.path(forResource: jsonName, ofType: "json") else {
observer(.error(SerializeError.missingJson(jsonName: jsonName)))
return Disposables.create()
}
do{
let data = try Data(contentsOf: URL(fileURLWithPath: path))
let entity = try JSONDecoder().decode(T.self, from: data)
observer(.success(entity))
} catch {
observer(.error(error))
}
return Disposables.create()
})
}
}
Return Entity created from
Stub JSON
Side Effect - Easy Unit Testing
FackObject
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Tips - Realtime update or not
lazy var realtimeRef: DatabaseReference = {
let ref = Database.database().reference()
ref.keepSynced(true)
return ref
}()
func getFavorite(userId: String) -> Single {
return realtimeRef.child(userId).child("favorites").get()
}
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Tips - Realtime update or not
lazy var realtimeRef: DatabaseReference = {
let ref = Database.database().reference()
ref.keepSynced(true)
return ref
}()
func getFavorite(userId: String) -> Single {
return realtimeRef.child(userId).child("favorites").get()
}
Reflect database update
immediately
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Pros/Cons
• Reduce building API man-hours
• No more performance tunings
• Easy to handle data in offline
Pros
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Pros/Cons
• Reduce building API man-hours
• No more performance tunings
• Easy to handle data in offline
Pros
#
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Pros/Cons
• Must have join logic in client side
• Need more money $ to build in some case
• Data cache system doesn’t suit for your app in some case
• Sorting and Query are hard to use
• Scaling requires sharding
(100,000 concurrent connections & 1,000 writes/sec.)
Cons
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Pros/Cons
• Must have join logic in client side
• Need more money $ to build in some case
• Data cache system doesn’t suit for your app in some case
• Sorting and Query are hard to use
• Scaling requires sharding
(100,000 concurrent connections & 1,000 writes/sec.)
Cons
%
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Alternatives
• Realtime Database + Cloud Functions
• Building API server (Old way)
• ???
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No content
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One more thing…
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Cloud Firestore
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• Stores data in documents organized in collections
• Sending data with protobuf, which have more types
• Introduced reference type, so requires less denormalization and data
flattening
• Indexed queries with compound sorting and filtering
Cloud Firestore
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Cloud Firestore
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Cloud Firestore
Reference type
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What will be changed on architecture
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
Presenter
View
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What will be changed on architecture
Entity
Data Access
Interface
Data Access
to Firebase
Interactor
Model
Presenter
View
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Recap
• Serverless architecture ( mBaaS / SaaS and etc. ) is also
effective to use on native apps
• API server can be replaced by Firebase Database / Cloud
firestore in some case
• Replaceable DAO and separate Entity and Model in app is
important
• With side effect, easy to test modules
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If you have Questions…
Daiki Matsudate
[email protected]
twitter: @d_date
GitHub: @d-date
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Enjoy! Your serverless
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References
• Clean Code: A Handbook of Agile Software Craftsmanship
by Robert C. Martin
• https://firebase.google.com/docs/firestore/rtdb-vs-firestore
• https://firebase.google.com/docs/firestore/firestore-for-
rtdb
• https://speakerdeck.com/bpyamasinn/api-wo-firebase-
realtime-database-niyi-xing-siteqi-fu-itakoto-ver2