Mixins over Inheritance Leveraging Mixins and Traits in Swift Olivier Halligon March 2017 aligatr 

aligatr Bonjour! • iOS Architect & Lead Dev @ Niji • Teaching, Sharing, Speaking
 http://alisoftware.github.io 
 @aligatr • OpenSource enthusiast
 http://github.com/AliSoftware
 OHHTTPStubs, SwiftGen, Reusable, CocoaPods, Fastlane !" #✍ %& '( 

aligatr Sci-Fi! 

aligatr Sci-Fi! Doc Emmett Brown Doctor Who Iron Man Superman Time Traveler Flyer Human Alien 

aligatr Inheritance? Doc Emmett Brown Doctor Who Iron Man Superman Human Alien Character 

aligatr Inheritance? Doc Emmett Brown Doctor Who Iron Man Superman Time Traveler Flyer Human Alien Character 

aligatr Composition! Doc Emmett Brown Doctor Who Iron Man Superman Time Machine Human Traits Alien Traits Flying Engine Flying Engine Time Machine Human Traits Alien Traits 

aligatr Composition! class DoctorWho { let traits: AlienTraits let tardis: TimeMachine let name: String init(name: String, planet: String = "Gallifrey") { self.traits = AlienTraits(planet: planet, hearts: 2) self.tardis = TimeMachine() self.name = name } } class TimeMachine { func travel(to date: Date) { print(")* \(date) +,") } } struct AlienTraits { let planet: String let hearts: Int } 

aligatr Composition! let david = DoctorWho() david.tardis.travel(to: Date(timeIntervalSince1970: 1303484520)) // )* Apr 22, 2011, 5:02 PM +, print(david.traits.hearts) // 2 let clark = SuperMan() clark.flyingEngine.fly() // flyingEngine?! ! - . 

aligatr Mixins? Doc Emmett Brown Doctor Who Iron Man Superman Time Traveler Flyer Human Alien Identity / 0 Abilities 

aligatr Protocols with Default Implementation protocol Flyer { func fly() }__ extension Flyer { func fly() { print("I believe I can flyyyyy ⽄") }__ }__ 

aligatr Protocols with Default Implementation protocol Flyer { func fly() }__ extension Flyer { func fly() { print("I believe I can flyyyyy ⽄") }__ }__ class SuperMan: Flyer { // let Clark sing! } class Bird: Flyer { // we get the default implementation of fly() here } class Plane: Flyer { // we get the default implementation of fly() here } I believe I can flyyyyy ⽄ 

aligatr Protocols with Default Implementation protocol Flyer { func fly() }__ extension Flyer { func fly() { print("I believe I can flyyyyy ⽄") }__ }__ class IronMan: Flyer { let thrusters = Thrusters() // specific implementation when needed func fly() { thrusters.start() } } 

aligatr Unlimited Abilities 0 protocol TimeTraveler { func travel(to date: Date) } extension TimeTraveler { func travel(to date: Date) { print(")* \(date) +,") } } protocol Flyer { func fly() }__ extension Flyer { func fly() { print("I believe I can flyyyyy ⽄") } } • • • 

aligatr One Identity, Multiple Abilities class TimeLord: Alien, TimeTraveler, Flyer { init() { super.init(name: "I'm the Doctor", planet: "Gallifrey") } } let doctorWho = TimeLord() doctorWho.travel(to: Date(timeIntervalSince1970: 1303484520)) // )* Apr 22, 2011, 5:02 PM +, doctorWho.fly() 

aligatr Adding Abilities extension TimeLord: SpaceTraveler {} extension Superman: SpaceTraveler {} protocol SpaceTraveler { func travel(to location: String) } extension SpaceTraveler { func travel(to location: String) { print("Let's go to \(location)!") } } doctorWho.travel(to: "Trenzalore") // prints "Let's go to Trenzalore!" 

aligatr Protocol All the Things! struct TimeLord: Alien, TimeTraveler, Flyer, SpaceTraveler { let name = "I'm the Doctor" let planet = "Gallifrey" } protocol Named { var name: String { get } } protocol Alien: Named { var planet: String { get } } class Character { let name: String init(name: String) { … } } class Alien: Character { let planet: String init(name: String, planet: String) { … } } « Protocol Oriented Programming is Not a Silver Bullet » — Chris Eidhof 

aligatr Back to Boring Reality class SuperSmartViewController: UIViewController, BurgerMenuProvider, Animatable, CustomTitleViewProvider { … } extension SuperSmartViewController: Themable { } let vc = SuperSmartViewController() vc.apply(theme: .dark) 

aligatr Creating type-safe APIs 

aligatr Creating type-safe APIs let cell1 = tableView.dequeueReusableCell(withIdentifier: "CustomCellOne", for: indexPath) as! CustomCellOne cell1.fill(withText: "Model One, \(indexPath.row)") class CustomCellOne: UITableViewCell { func fill(withText: String) { } } class CustomCellTwo: UITableViewCell { func fill(withIndex: Int) { } } 

aligatr Creating type-safe APIs protocol Reusable: class { static var reuseIdentifier: String { get } } extension Reusable { static var reuseIdentifier: String { return String(describing: Self.self) } } let cell1 = tableView.dequeueReusableCell(withIdentifier: CustomCellOne.reuseIdentifier, for: indexPath) as! CustomCellOne cell1.fill(withText: "Model One, \(indexPath.row)") class CustomCellOne: UITableViewCell, Reusable { func fill(withText: String) { } } class CustomCellTwo: UITableViewCell, Reusable { func fill(withIndex: Int) { } } 

aligatr Creating type-safe APIs protocol Reusable: class { static var reuseIdentifier: String { get } } extension Reusable { static var reuseIdentifier: String { return String(describing: Self.self) } } extension UITableView { func dequeueReusableCell(indexPath: IndexPath) -> T { return self.dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T } } class CustomCellOne: UITableViewCell, Reusable { func fill(withText: String) { } } class CustomCellTwo: UITableViewCell, Reusable { func fill(withIndex: Int) { } } 

aligatr Creating type-safe APIs protocol Reusable: class { static var reuseIdentifier: String { get } } extension Reusable { static var reuseIdentifier: String { return String(describing: Self.self) } } extension UITableView { func dequeueReusableCell(indexPath: IndexPath) -> T where T: UITableViewCell, T: Reusable { return self.dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T } } class CustomCellOne: UITableViewCell, Reusable { func fill(withText: String) { } } class CustomCellTwo: UITableViewCell, Reusable { func fill(withIndex: Int) { } } 

aligatr Creating type-safe APIs extension UITableView { func dequeueReusableCell(indexPath: IndexPath) -> T where T: UITableViewCell, T: Reusable { return self.dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T } } let cell1 = tableView.dequeueReusableCell(indexPath: indexPath) cell1.fill(withText: "Model One, \(indexPath.row)") error: generic parameter 'T' could not be inferred 

aligatr Creating type-safe APIs extension UITableView { func dequeueReusableCell(indexPath: IndexPath) -> T where T: UITableViewCell, T: Reusable { return self.dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T } } let cell1: CustomCellOne = tableView.dequeueReusableCell(indexPath: indexPath) cell1.fill(withText: "Model One, \(indexPath.row)") 

aligatr Creating type-safe APIs extension UITableView { func dequeueReusableCell(indexPath: IndexPath) -> T where T: UITableViewCell, T: Reusable { return self.dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T } } let cell1: CustomCellOne = tableView.dequeueReusableCell(indexPath: indexPath) cell1.fill(withText: "Model One, \(indexPath.row)") let cell2 = tableView.dequeueReusableCell(indexPath: indexPath) as CustomCellTwo cell2.fill(withIndex: indexPath.row) 

aligatr Creating type-safe APIs class CustomCellOne: UITableViewCell, Reusable { func fill(withText: String) { } } class CustomCellTwo: UITableViewCell, Reusable { func fill(withIndex: Int) { } } let cell1: CustomCellOne = tableView.dequeueReusableCell(indexPath: indexPath) cell1.fill(withText: "Model One, \(indexPath.row)") let cell2 = tableView.dequeueReusableCell(indexPath: indexPath) as CustomCellTwo cell2.fill(withIndex: indexPath.row) 

aligatr Thank You! protocol Talk { func ask(question: String) -> String } extension Talk { func ask(question: String) -> String { return "ya tu sabes" } } http://alisoftware.github.io https://twitter.com/aligatr http://github.com/AliSoftware/Reusable ✍ March 2017 Olivier Halligon I believe I can flyyyyy ⽄