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MIXINS OVER INHERITANCE
Leveraging Mixins and Traits in Swift
Olivier Halligon September 2016
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• iOS Architect
Niji
• Teaching, Sharing, Speaking
http://alisoftware.github.io
https://twitter.com/aligatr
• OpenSource enthusiast
http://github.com/AliSoftware
OHHTTPStubs, SwiftGen, Dip, Reusable, CocoaPods…
HELLO WORLD!
✍
%
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THE PROBLEM
class BurgerViewController: UIViewController {
func setupBurgerMenu() { … }
override func viewDidLoad() {
super.viewDidLoad()
setupBurgerMenu()
}
}
class MyViewController1: BurgerViewController {
…
}
class MyViewController2: BurgerViewController {
…
}
class MyViewController3: UITableViewController + BurgerViewController {
…
}
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COMPOSITION!
class BurgerMenuManager {
func setupBurgerMenu() { … }
func onBurgerMenuTapped() { … }
var burgerMenuIsOpen = false {
didSet { … }
}
}
class MyViewController1: UIViewController {
let menuManager = BurgerMenuManager()
override func viewDidLoad() {
super.viewDidLoad()
menuManager.setupBurgerMenu()
}
}
class MyViewController3: UITableViewController {
let menuManager = BurgerMenuManager()
override func viewDidLoad() {
super.viewDidLoad()
menuManager.setupBurgerMenu()
}
}
class MyViewController2: UIViewController {
let menuManager = BurgerMenuManager()
override func viewDidLoad() {
super.viewDidLoad()
menuManager.setupBurgerMenu()
}
}
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MIXINS & TRAITS
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MIXINS & TRAITS
Doc Emmett Brown
Doctor Who
Iron Man
Superman
Time Traveler
Flyer
Human
Alien
Identities Abilities
Inheritance let you describe what an object is.
Traits let you describe what an object can do.
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PROTOCOLS
WITH DEFAULT IMPLEMENTATION
protocol TimeTraveler {
func travel(to: NSDate)
}__
extension TimeTraveler {
func travel(to: NSDate) {
print(" \(date) ")
}__
}__
class TimeLord: TimeTraveler {
// we don't need to implement travel(to:) there
}
let doctorWho = TimeLord()
doctorWho.travel(to: NSDate(timeIntervalSince1970: 1303484520))
// prints " Apr 22, 2011, 5:02 PM "
let docBrown = DocEmmettBrown()
docBrown.travel(to: NSDate(timeIntervalSince1970: 499161600))
// prints " Oct 26, 1985, 9:00 AM "
class DocEmmettBrown: TimeTraveler {
// we don't need to implement travel(to:) there
}
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ONE IDENTITY, MULTIPLE ABILITIES
protocol Flyer {
func fly()
}
extension Flyer {
func fly() {
print("I believe I can flyyyyy ⽄")
}
}
class Character {
let name: String
init(name: String) { … }
}
class Human: Character {
let country: String
init(name: String, country: String = "") { … }
}
class Alien: Character {
let planet: String
init(name: String, planet: String) { … }
}
Identities Abilities
protocol TimeTraveler {
func travel(to: NSDate)
}__
extension TimeTraveler {
func travel(to: NSDate) {
print(" \(date) ")
}__
}__
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ONE IDENTITY, MULTIPLE ABILITIES
protocol Flyer {
func fly()
}
protocol TimeTraveler {
func travel(to: NSDate)
}
class Character {
let name: String
}
class Human: Character {
let country: String
}
class Alien: Character {
let planet: String
}
class TimeLord: Alien, TimeTraveler {
init() {
super.init(name: "I'm the Doctor", planet: "Gallifrey")
}
}
class DocEmmettBrown: Human, TimeTraveler {
init() {
super.init(name: "Emmett Brown", country: "USA")
}
}
class Superman: Alien, Flyer {
init() {
super.init(name: "Clark Kent", planet: "Krypton")
}
}
class IronMan: Human, Flyer {
init() {
super.init(name: "Tony Stark", country: "USA")
}
}
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ADDING ABILITIES
extension TimeLord: SpaceTraveler {}
extension Superman: SpaceTraveler {}
protocol SpaceTraveler {
func travel(to: String)
}
extension SpaceTraveler {
func travel(to: String) {
print("Let's go to \(location)!")
}
}
doctorWho.travel(to: "Trenzalore")
// prints "Let's go to Trenzalore!"
class TimeLord:
Alien, TimeTraveler
class DocEmmettBrown:
Human, TimeTraveler
class Superman:
Alien, Flyer
class IronMan:
Human, Flyer
class Character
class Human: Character
class Alien: Character
protocol Flyer {
func fly()
}
protocol TimeTraveler {
func travel(to: NSDate)
}
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REAL-LIFE EXAMPLE
class CustomCellOne: UITableViewCell {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell {
func fill(withIndex: Int) { }
}
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REAL-LIFE EXAMPLE
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
let type: Reusable.Type = CustomCellOne.self
tableView.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath)
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: Reusable.Type)
-> UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath)
}
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath, type: CustomCellOne.self)
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
UITableViewCell
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type)
-> UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath)
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath, type: CustomCellOne.self)
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type)
-> T
where T: UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath) as! T
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath, type: CustomCellOne.self)
cell1.fill(withText: "Hello there!")
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type = T.self)
-> T
where T: UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath) as! T
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath, type: CustomCellOne.self)
cell1.fill(withText: "Hello there!")
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type = T.self)
-> T
where T: UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath) as! T
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath)
cell1.fill(withText: "Hello there!")
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type = T.self)
-> T
where T: UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath) as! T
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath) as CustomCellOne
cell1.fill(withText: "Hello there!")
protocol Reusable: class {
static var reuseIdentifier: String { get }
}
extension Reusable {
static var reuseIdentifier: String {
return String(reflecting: Self.self)
}
}
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REAL-LIFE EXAMPLE
extension UITableView {
func dequeueReusableCell(indexPath: IndexPath, type: T.Type = T.self)
-> T
where T: UITableViewCell {
return self.dequeueReusableCell(withIdentifier: type.reuseIdentifier,
for: indexPath) as! T
}
}
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { }
}
class CustomCellTwo: UITableViewCell, Reusable {
func fill(withIndex: Int) { }
}
let cell1 = tableView.dequeueReusableCell(indexPath: indexPath) as CustomCellOne
cell1.fill(withText: "Hello there!")
let cell2: CustomCellTwo = tableView.dequeueReusableCell(indexPath: indexPath)
cell2.fill(withIndex: indexPath.row)
tableView.register(class: CustomCellOne.self)
✨
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REAL-LIFE EXAMPLE
class CustomCellOne: UITableViewCell, Reusable {
func fill(withText: String) { … }
}
class CustomXIBCell: UICollectionViewCell, NibReusable {
func fill(indexPath: NSIndexPath) { … }
}
class InfoViewController: UIViewController, StoryboardBased {
…
}
let infoVC = InfoViewController.instantiate()
infoVC.setInfo(self.info)
class MyCustomWidget: UIView, NibOwnerLoadable {
@IBInspectable var rectColor: UIColor?
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
MyCustomWidget.loadFromNib(owner: self)
}
}
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THANK YOU
protocol Talk {
func ask(question: String)
-> String
}
extension Talk {
func ask(question: String)
-> String {
return "42"
}
}
• http://github.com/AliSoftware/Reusable
• http://alisoftware.github.io
• https://twitter.com/aligatr
✍
FrenchKit
September 2016
Olivier Halligon