Why the Dark Side should use Swift and a SOLID Architecture

Jorge D. Ortiz-Fuentes @jdortiz

#SwiftDarkSide

A Canonical Examples

production

#SwiftDarkSide

#SwiftDarkSide

Agenda

The Weaknesses of the Dark Side

SOLID Architecture

Design patterns

Weaknesses of the Dark

Side

Conspiracy Theory

Agility and the MVP

Moving a Planet

SPoF

Whose blame is that?

Framework dependency

Teams can hardly work together

Do you see any

problems?

#SwiftDarkSide

Needs to Address

Fast growth

Robustness

testable

decoupled

debuggable (blame)

Team collaboration

Reusable

Defer decisions

Replaceable frameworks

There is a way: SOLID Principles

AKA Clean

Architecture

I find your lack of faith disturbing

SOLID Architecture

Clean ArchitectureAppDelegate

View (VC) Presenter Interactor Entity Gateway

Connector

#SwiftDarkSide

Single Responsibility

MVC is not enough

More classes, but more cohesive: only one reason to change

#SwiftDarkSide

Business Logicimport Foundation

class ShowAllSpeakersInteractor {

// MARK: - Properties let entityGateway: EntityGatewayFetchSpeakersProtocol weak var presenter: SpeakersListPresenterProtocol?

// MARK: - Initializers init(entityGateway: EntityGatewayFetchSpeakersProtocol) { self.entityGateway = entityGateway } }

extension ShowAllSpeakersInteractor: InteractorCommandProtocol { func execute() { let entities = entityGateway.fetchAllSpeakers() let displayData = entities.map({entity in return SpeakerDisplayData(speaker: entity)}) presenter?.presentAllSpeakers(displayData) } }

#SwiftDarkSide

Open Close

Open to Extension, Closed to Modification

#SwiftDarkSide

class SpeakersTableViewController: UITableViewController, SegueHandlerTypeProtocol { static let speakerCellIdentifier = "SpeakerCell" var eventHandler: SpeakersListEventHandlerProtocol? var numberOfRows = 0 override func viewDidLoad() { super.viewDidLoad() eventHandler?.viewDidLoad() }

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return numberOfRows }

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier(SpeakersTableViewController.speakerCellIdentifier, forIndexPath: indexPath) as! SpeakerTableViewCell eventHandler?.presentCell(cell, indexPath: indexPath) return cell } }

extension SpeakersTableViewController: SpeakersListViewProtocol { func configureListWithNumberOfRows(numberOfRows: Int) { self.numberOfRows = numberOfRows }

func addRowsAtIndexPaths(indexPaths:[NSIndexPath]) { self.tableView.insertRowsAtIndexPaths(indexPaths, withRowAnimation: UITableViewRowAnimation.Automatic) } }

Passive View

#SwiftDarkSide

Liskov Substitution

It should be possible to use derived classes without special care

#SwiftDarkSide

extension SpeakersListsPresenter: SpeakersListEventHandlerProtocol { func viewDidLoad() { interactor.execute() }

func presentCell(cell: SpeakerCellProtocol, indexPath: NSIndexPath) { let index = indexPath.row guard index < speakers.count else { return } let speaker = speakers[index] cell.displayName(speaker.name) cell.displayTitle(speaker.title) cell.displayDateSubmitted(relativeDateStringFromDate(speaker.dateSubmitted)) } }

Presentationclass SpeakersListsPresenter { weak var view: SpeakersListViewProtocol? let interactor: ShowAllSpeakersInteractor private var speakers: [SpeakerDisplayData]=[]

// MARK: - Initializer init(interactor: ShowAllSpeakersInteractor, deleteInteractor: DeleteSpeakerInteractorProtocol) { self.interactor = interactor } }

extension SpeakersListsPresenter: SpeakersListPresenterProtocol { func presentAllSpeakers(speakers: [SpeakerDisplayData]) { view?.configureListWithNumberOfRows(speakers.count) self.speakers = speakers let addedIndexPaths = speakers.enumerate() .map({(index, _) in return NSIndexPath(forRow: index, inSection: 0)}) view?.addRowsAtIndexPaths(addedIndexPaths) } }

#SwiftDarkSide

Interface Segregation

Dont force a class to depend on methods that it wont use

One interactor will not likely use every functionality of the entity gateway

#SwiftDarkSide

class InMemorySpeakersRepo { // MARK: - Properties var speakers: [Speaker] = [] init() { } }

extension InMemorySpeakersRepo: EntityGatewayFetchSpeakersProtocol { func fetchAllSpeakers() -> [Speaker] { return speakers } }

extension InMemorySpeakersRepo: EntityGatewayCreateSpeakerProtocol { func createSpeaker(name name: String, title: String, synopsis: String, dateSubmitted: NSDate) { let id = IdentityGenerator.newUUID() speakers.append(Speaker(id: id, name: name, title: title, synopsis: synopsis, dateSubmitted: dateSubmitted)) } }

extension InMemorySpeakersRepo: EntityGatewayDeleteSpeakerProtocol { func deleteSpeaker(id: String) { speakers = speakers.filter { speaker in speaker.id != id } } }

Different Functions of the Entity Gateway

#SwiftDarkSide

Dependency Inversion

The business case SHOULDNT depend on the frameworks

#SwiftDarkSide

Deletion Use Caseclass DeleteSpeakerInteractor { let entityGateway: EntityGatewayDeleteSpeakerProtocol var id: String?

init(entityGateway: EntityGatewayDeleteSpeakerProtocol) { self.entityGateway = entityGateway } }

extension DeleteSpeakerInteractor : InteractorCommandProtocol { func execute() { guard let id = self.id else { return } entityGateway.deleteSpeaker(id) } }

Design Patterns

Take me Outta Herefunc presentCell(cell: SpeakerCellProtocol, indexPath: NSIndexPath) { let index = indexPath.row guard index < speakers.count else { return } let speaker = speakers[index] cell.displayName(speaker.name) cell.displayTitle(speaker.title) cell.displayDateSubmitted(relativeDateStringFromDate(speaker.dateSubmitted)) }

Know

That!

var control = Houston(fuel: 1.0, astronaut: nil, spaceshipOK: true)

do { try control.launchSpaceship() } catch Houston.LaunchError.NoFuel { // Add Fuel print("Adding fuel") } catch Houston.LaunchError.NoAstronaut { print("Next in line") } catch Houston.LaunchError.BrokenShip(let problem) { print(problem) } catch let unknowError { // }

Ready for Lifeclass Houston { let fuel: Double let astronaut: String let spaceshipOK: Bool init (fuel: Double, astronaut: String?, spaceshipOK: Bool) { self.fuel = fuel self.astronaut = astronaut ?? "" self.spaceshipOK = spaceshipOK } enum LaunchError: ErrorType { case NoFuel, NoAstronaut, BrokenShip(String) } func launchSpaceship() throws { guard fuel >= 1.0 else { throw LaunchError.NoFuel } guard astronaut != "" else { throw LaunchError.NoAstronaut } guard spaceshipOK else { throw LaunchError.BrokenShip("Engine") } print("Launching spaceship") } }

Know

That!

class Text { func displayContents() { print("Hola") } }

class NullText: Text { override func displayContents() { print(Not much here") } }

func fetchText() -> Text { return NullText() }

let text = fetchText() text.displayContents()

Null Objectclass Text { func displayContents() { print("Hola") } }

func fetchText() -> Text? { return nil }

if let text = fetchText() { text.displayContents() }

Poor Templateclass PoorTrooper { func getIntoSpaceShip() { print("Commencing countdown engines on") }

func conquer(target: String) { fatalError() }

func comeBack() { print("Planet earth is blue") }

func attack(target: String) { getIntoSpaceShip() conquer(target) comeBack() } }

let cloneTrooper = PoorTrooper() cloneTrooper.attack("Alderaan")

Swifty Templateprotocol Trooper { func getIntoSpaceShip() func conquer(target: String) func comeBack() func attack(target: String) }

extension Trooper { func getIntoSpaceShip() { print("Commencing countdown engines on") }

func comeBack() { print("Planet earth is blue") }

func attack(target: String) { getIntoSpaceShip() conquer(target) comeBack() } }

class StormTrooper: Trooper { func conquer(target: String) { print("Become part of the Empire, \(target)") } }

let finn = StormTrooper() finn.attack("Tatooine")

Next Steps

#SwiftDarkSide

RecommendationsPay attention to your architecture; It always pays off

Use Principles to take decisions

Take advantage of the language and adapt the patterns to it

In case of doubt, ask for an architecture loan and ship it

canonicalexamples.com coupon:

APPSTERDAMERS16

http://canonicalexamples.com

Thank you!

@jdortiz #SwiftDarkSide