These are the slides of my talk at iOSCon 2017: https://skillsmatter.com/skillscasts/9549-architecting-alive-apps Our apps are ever more alive. They interact with the rest of the world talking to backends and receiving notifications from them. They get their input from us and from other sensors. They are even aware of the location of the device they run in, or its position. But, in our IoT world, they may also detect presence in a room, get the temperature of it, or change the color of its lights. Sadly enough, many of the apps available today with those capabilities have some architectural limitations: Many of them are written in a way that is really dependent on a specific hardware. Some restrict their use cases to whatever is provided by the hardware devices. And almost all of them expect having a connection with the real device as the only way to test if they work properly. However, we can also use an advanced architecture, like the Clean Architecture, to create a beautiful, scalable, testable, and robust application. Join Jorge and he will share with you how you can do it! This is a "Code or it didn't happen" (TM) talk.

1. #Swift3Arch
Architecting Alive
Apps
Jorge D. Ortiz Fuentes
@jdortiz

2. #Swift3CA
A Canonical
Examples
Production

3. #Swift3CA
Agenda
★ Advanced Architecture Background
★ Application for Frameworks
★ Real World Example
★ Recommendations
★ Recap

4. Advanced Architecture

5. The Classics

6. #Swift3Arch
Clean Architecture: iOS
App
Delegate
View (VC) Presenter Interactor
Entity
Gateway
Connector

7. #Swift3Arch
Clean Architecture Layers
UI
DB
Preseters
Gateways
Use
cases
Entities
D
ependencies

8. #Swift3CA
View
class AddProgrammerViewController: UITableViewController, UITextFieldDelegate {
var presenter: AddProgrammerPresenter!
var connector: AddProgrammerConnector!
@IBOutlet weak var nameTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
presenter.viewReady()
}
@IBAction func cancel(_ sender: Any) { presenter.cancel() }
@IBAction func save(_ sender: Any) { presenter.save() }
}
extension AddProgrammerViewController: AddProgrammerView {
func display(title: String) { self.title = title }
func enableSaveButton(_ enable: Bool) { saveButton.isEnabled = enable }
}

9. #Swift3CA
Presenter
class AddProgrammerPresenter {
private let useCaseFactory: UseCaseFactory
weak var view: AddProgrammerView!
private var programmer = ProgrammerRequest() {
didSet { updateView() }
}
init(useCaseFactory: UseCaseFactory) { self.useCaseFactory = useCaseFactory }
func viewReady() { configureView() }
private func updateView() {
showTitle()
!// …
configureSaveAbility()
}
private func configureView() {
setUpName()
!// …
updateView()
}
private func showTitle() { view.display(title: programmer.name) }
}

10. #Swift3CA
Interactor
class AddProgrammerUseCase {
fileprivate let entityGateway: EntityGateway
fileprivate let request: ProgrammerRequest
fileprivate let completion: AddProgrammerCompletion
init(entityGateway: EntityGateway, request: ProgrammerRequest, completion:
@escaping AddProgrammerCompletion) {
self.entityGateway = entityGateway
self.request = request
self.completion = completion
}
}
extension AddProgrammerUseCase: UseCase {
func execute() {
let programmer = Programmer(…)
entityGateway.create(programmer: programmer) {
self.completion()
}
}
}

11. #Swift3CA
Entity Gateway
class InMemoryRepo {
var fetchNotifier: FetchProgrammersCompletion?
fileprivate var programmers = […]
}
extension InMemoryRepo: EntityGateway {
func create(programmer: Programmer, completion: @escaping
CreateProgrammerCompletion) {
programmers.append(programmer)
completion()
self.fetchNotifier?(programmers)
}
}

12. #Swift3CA
Connector
class AddProgrammerConnector {
let entityGateway: EntityGateway
init(entityGateway: EntityGateway) {
self.entityGateway = entityGateway
}
func assembleModule(view: AddProgrammerViewController) {
let useCaseFactory = UseCaseFactory(entityGateway: entityGateway)
let presenter = AddProgrammerPresenter(useCaseFactory: useCaseFactory)
view.presenter = presenter
view.connector = self
presenter.view = view
}
}

13. #Swift3CA
Factory
class UseCaseFactory {
let entityGateway: EntityGateway
init(entityGateway: EntityGateway) {
self.entityGateway = entityGateway
}
func addProgrammerUseCase(request: ProgrammerRequest, completion: @escaping
AddProgrammerCompletion) !-> UseCase {
return AddProgrammerUseCase(entityGateway: entityGateway, request:
request, completion: completion)
}
}

14. And What If?

15. #Swift3CA
Interacting with
Frameworks
Accounts
AddressBook
HomeKit
EventKit
HealthKit
Core Audio
Core Location
HomeKit
EventKit

16. The Secret Sauce

17. #Swift3CA
Injecting Dependencies
View
Presenter
UseCaseFactory
Entity
Gateway
Connector

18. Been There, Done
That

19. Dependency Inversion
Principle
High LowAbstract
Low

20. #Swift3CA
CloudKit
★ This is data source
using CloudKit
★ CloudKit is an
implementation
detail
★ NO leaky
abstractions
class CloudKitRepo {
let database: CKDatabase
let programmerRecord = "Programmer"
init() {
let container = CKContainer.default()
database = container.database(with: .private)
}
fileprivate func recordFrom(programmer: Programmer) !->
CKRecord {
let programmerID = CKRecordID(recordName:
programmer.id)
let record = CKRecord(recordType: programmerRecord,
recordID: programmerID)
updateRecordProperties(record: record, programmer:
programmer)
return record
}
}
extension CloudKitRepo: EntityGatewayProtocol {
func create(programmer: Programmer, completion:@escaping ()
!-> Void) {
let record = recordFrom(programmer: programmer)
database.save(record) { record, error in
guard error !== nil else {
NSLog("Save error:
(error!?.localizedDescription)")
return
}
DispatchQueue.main.sync { completion() }
}
}
}

21. #Swift3CA
Injecting Dependencies 2
View
Presenter
UseCaseFactory
Entity
Gateway
Connector
Framework

22. Real World Example

23. A Prototype

24. #Swift3CA
Meetinator
EventKit
HomeKit
Magic

25. #Swift3CA
Yes, but…

26. #Swift3CA
MQTT
Server
Suscribe
“/rooms/meeting1/colorlight”
Device
Raspberry
Pi
Device
Device

27. #Swift3CA
MQTT
Server
Publish
“/rooms/meeting1/colorlight”
{ “firetime”: …}
Device
Raspberry
Pi
Device
Device
iPhone

28. #Swift3CA
Another Approach
EventKit
CocoaMQTT MQTT
(JSON)
Mosquitto

29. Right Abstraction?

30. #Swift3CA
Any* Abstraction is
Better than No
Abstraction

31. Hints for Good
Abstractions

32. #Swift3CA
No References to
Framework

33. #Swift3CA
Use Your Own Data
Types

34. #Swift3CA
Events
struct MeetingEvent {
let id: String
var name: String
var startDate: Date
var endDate: Date
var hasLights: Bool
}

35. #Swift3CA
Use Your Own
Communication
(Delegates/Observer/Rx…)

36. #Swift3CA
Use Only What You
Need

37. #Swift3CA
Move Implementation
Details Into
Abstracted Type

38. Details

39. #Swift3CA
From Date to JSON
★ MQTT messages
contained JSON
★ firetime is a JSON
format date
let formatter =
ISO8601DateFormatter()
let command: [ String: String ] = [
"firetime":
formatter.string(from: fireDate),
"type": type.mqttActionType(),
]
let jsonData = try!
JSONSerialization.data(withJSONObject
: command, options:
JSONSerialization.WritingOptions())
as Data

40. #Swift3CA
Picky with Dates
★ HomeKit
HMTimeTrigger only
accepts times with
seconds = 0
private func fixFireDate(_ fireDate:
Date) !-> Date {
let calendar = Calendar.current
let fixedFireDate =
calendar.nextDate(after: fireDate,
matching: DateComponents(second: 0),
matchingPolicy: .nextTime)!
return fixedFireDate
}

41. #Swift3CA
Browse HomeKit
★ HomeKit offers several
abstractions in a
hierarchy
• Homes
• Rooms
• Accessories
• Services
• Triggers
★ Extract what you need
class HomeKitColorLight: NSObject, LightController
{
var delegate: LightControllerDelegate?
fileprivate let homeManager: HMHomeManager
fileprivate var primaryHome: HMHome?
func homeManagerDidUpdateHomes(_ manager:
HMHomeManager) {
primaryHome = homeManager.primaryHome
delegate!?.lightControllerReady(self)
}
private func searchFirstColorLight() !->
HMService? {
let lightbulbs =
primaryHome!?.servicesWithTypes([HMServiceTypeLightb
ulb])
let colorLightbulb = lightbulbs!?.first
{ (service) in
let characteristics =
service.characteristics.filter { (characteristic)
in
return
characteristic.characteristicType !==
HMCharacteristicTypeHue
}
return characteristics.count > 0
}
return colorLightbulb
}
}

42. #Swift3CA
Look for Events
★ EventKit allows
multiple calendars
★ Avoid that
complexity
fileprivate func fetchMeetingCalendar() {
guard status !== .ready else { return }
let calendars =
eventStore.calendars(for: .event)
let calendar = calendars.filter { $0.title
!== meetingCalendarTitle } .first
if let calendar = calendar {
meetingCalendar = calendar
} else {
meetingCalendar =
EKCalendar(for: .event, eventStore:
eventStore)
if let meetingCalendar =
meetingCalendar {
meetingCalendar.title =
meetingCalendarTitle
meetingCalendar.source =
eventStore.defaultCalendarForNewEvents.source
do {
try
eventStore.saveCalendar(meetingCalendar,
commit: true)
} catch let error as NSError {
NSLog("Error: (error)")
}
}
}
}

43. #Swift3CA
Authorization
★ EventKit requires
Authorization to
access the data
class EventKitEventProvider {
enum Status {
case ready, accessDenied, unknown
}
let eventStore: EKEventStore
var status = Status.unknown
init() {
eventStore = EKEventStore()
checkAccessToEvents()
fetchMeetingCalendar()
}
private func checkAccessToEvents() {
switch
EKEventStore.authorizationStatus(for: .event) {
case .authorized:
status = .ready
case .notDetermined: !// First time access
requestAccessToEvents()
case .denied, .restricted:
status = .accessDenied
}
}
private func requestAccessToEvents() {
eventStore.requestAccess(to: .event)
{ (granted: Bool, error: Error?) in
!// …
}
}
}

44. #Swift3CA
extension LightControllerAction {
func homeKitColor() !-> UIColor {
let color: UIColor
switch(self) {
case .start: color = UIColor.green
case .warn: color =
UIColor.orange
case .end: color = UIColor.red
case .off: color = UIColor.black
}
return color
}
func sceneName() !-> String {
let name: String
switch(self) {
case .start: name = "Go green"
case .warn: name = "Go orange"
case .end: name = "Go red"
case .off: name = "Go off"
}
return name
}
}
Extend like a Boss
extension LightControllerAction {
func mqttActionType() !-> String {
let action: String
switch self {
case .start:
action = "start"
case .warn:
action = "warn"
case .end:
action = "end"
case .off:
action = "off"
}
return action
}
}

45. Recap

46. #Swift3CA
Recap
★ IoT is cool!
★ Advanced architectures can also be applied
to apps with frameworks
★ Use abstractions
★ YES, I mean it: Use abstractions

47. Thank
You!

48. @jdortiz
#Swift3CA