Swift - Beyond Beginner

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DEVNEXUS Atlanta – February 22, 2018 Swift Patrick Seda - @pxtrick

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Target Tools

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Beginner Target Tools @pxtrick

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Target Tools @pxtrick “Beyond Beginner” This

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Background

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Background @pxtrick “The Effects of RR-Interval Data on Heart Rate Variability and Congestive Heart Failure” Then: Now: Mobile and Web Business Apps Atlanta-ish, GA @pxtrick Patrick Seda Increasing the Quality of the Universe

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Access Control

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public open internal fileprivate private Access Control @pxtrick

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file 2 class A class B file 1 module “consumer” Access Control @pxtrick class C

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file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { private var value } Access Control @pxtrick class C

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file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { fileprivate var value } Access Control @pxtrick class C

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class C file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { internal var value } Access Control @pxtrick

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file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { public var value // Accessible, no override } Access Control @pxtrick class C

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file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { open var value // Accessible, can override } Access Control @pxtrick class C

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Most restrictive Least restrictive Access Control @pxtrick

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-open -public -internal -fileprivate -private Access Control @pxtrick Most restrictive Least restrictive Default!

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Why is the default level internal? “When you write a simple single-target app, the code in your app is typically self-contained within the app and doesn’t need to be made available outside of the app’s module. The default access level of internal already matches this requirement. Therefore, you don’t need to specify a custom access level.” Because: Less typing for small apps! Access Control @pxtrick

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-open -public -internal -fileprivate -private What should we do? Access Control @pxtrick Most restrictive Least restrictive

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Named Model Types

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enum vs. struct vs. class Named Model Types @pxtrick

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enum Named Model Types @pxtrick

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// Modeling a Finite-State Machine. // State of the system. enum AlarmState { case disarmed case armed case alarming } // System-wide events. enum Event { case arm case disarm case tripSensor } Named Model Types @pxtrick

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var currentState: AlarmState func handleEvent(_ event: Event) { switch event { case .arm: if (currentState == .disarmed) { currentState = .armed } case .disarm: currentState = .disarmed case .tripSensor: if (currentState == .armed) { currentState = .alarming } } } Named Model Types @pxtrick

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var currentState: AlarmState = .disarmed handleEvent(.arm) // currentState == .armed handleEvent(.tripSensor) // currentState == .alarming handleEvent(.disarm) // currentState == .disarmed handleEvent(.tripSensor) // currentState == .disarmed Named Model Types @pxtrick

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// Define some Gibson guitar types enum Gibson: String { case lesPaul case es355 case flyingV case sg } Named Model Types @pxtrick

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// Define some Gibson guitar types enum Gibson: String { case lesPaul case es355 case flyingV case sg } let myGuitar = Gibson.lesPaul print("My guitar is a \(myGuitar.rawValue)") let yourGuitar: Gibson = .flyingV print("Your guitar is a \(yourGuitar.rawValue)") My guitar is a lesPaul Your guitar is a flyingV Named Model Types @pxtrick Ou t p u t :

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// Define some Gibson guitar types enum Gibson: String { case lesPaul = "Les Paul" case es355 = "ES355" case flyingV = "Flying V" case sg = "SG" } let myGuitar = Gibson.lesPaul print("My guitar is a \(myGuitar.rawValue)") let yourGuitar: Gibson = .flyingV print("Your guitar is a \(yourGuitar.rawValue)") My guitar is a Les Paul Your guitar is a Flying V Named Model Types @pxtrick Ou t p u t :

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struct & class Named Model Types @pxtrick

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When should we use struct vs. class? “In all other cases, define a class, and create instances of that class to be managed and passed by reference. In practice, this means that most custom data constructs should be classes, not structures.” Use a struct when: - Encapsulate few, simple data values - Data can be copied (passed by value) - Does not need inheritance Named Model Types @pxtrick

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Protocols for Design

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Let’s Design A game! Protocols for Design @pxtrick

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Protocols for Design @pxtrick

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Design before coding! Protocols for Design @pxtrick

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Musician Musical Instrument Stringed Instrument Cello Viola Violin Bass makeSound() numStrings perform() Protocols for Design @pxtrick

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protocol MusicalInstrument { func makeSound() } protocol StringedInstrument: MusicalInstrument { var numStrings: Int { get } } extension StringedInstrument { func makeSound() { print("Plink") } } class Cello: StringedInstrument { var numStrings: Int = 4 func makeSound() { print(”Hurrm Hummm") } } class Bass: StringedInstrument { var numStrings: Int = 4 func makeSound() { print("A Boom Boom Boom") } } Protocols for Design @pxtrick

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class Musician { var instrument: MusicalInstrument? func perform() { instrument?.makeSound() } } let cello: MusicalInstrument = Cello() let bass: MusicalInstrument = Bass() let musician = Musician() musician.instrument = cello musician.perform() musician.instrument = bass musician.perform() Hurrm Hummm A Boom Boom Boom Protocols for Design @pxtrick Ou t p u t :

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CLosures

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callbacks Closures @pxtrick

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// Do some stuff and then fire a callback. func doSomething( /* ??? */ ) { // ... onDone() } Closures - C a l lb a cks @pxtrick

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// Increment an integer and fire a callback. func increment(_ value: inout Int, onDone onDone: () -> Void) { value += 1 onDone() } // Define our callback. var attentionCb = { print("Attention! value = \(value)") } // Test it out. var value = 3; increment(&value, onDone: attentionCb) increment(&value, onDone: attentionCb) Attention! value = 4 Attention! value = 5 @pxtrick Ou t p u t : Closures - C a l lb a cks

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time of execution Closures @pxtrick

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var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: () -> Void) { queue.sync { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) Work item 1 Work item 2 @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion

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var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: () -> Void) { queue.async { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) error: closure use of non-escaping parameter 'work' may allow it to escape @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion

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var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: @escaping () -> Void) { queue.async { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) Work item 2 Work item 1 @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion

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Closure Expressions Closures @pxtrick

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Define a normal comparison function. func backwards(_ s1: String, _ s2: String) { return s1 > s2 } // Execute the array sort. var reversedOrder = cities.sorted(by: backwards) print("\(reversedOrder)") ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Closure Expression syntax. var reversedOrder = cities.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Inferring type from context. var reversedOrder = cities.sorted(by: { s1, s2 in return s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Implicit returns from single-expression closures. var reversedOrder = cities.sorted(by: { s1, s2 in s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Shorthand argument names. var reversedOrder = cities.sorted(by: { $0 > $1 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s

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let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Operator methods. var reversedOrder = cities.sorted(by: >) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : // Closure Expression syntax. var reversedOrder = cities.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 }) Previously: Closures - C l os u r e E xp r e s s io n s

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Memory Leaks

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ARC – Automatic Reference Counting Memory Leaks @pxtrick

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// A rockin’ band. class RockBand { var keys: Keyboard? deinit { print("[RockBand] - deinit()") } } // A tasty delight. class Keyboard { var band: RockBand? deinit { print("[Keyboard] - deinit()") } } Memory Leaks @pxtrick

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// Create our band. var band: RockBand? = RockBand() // Create our keys. var keys: Keyboard? = Keyboard() // Establish a beautiful friendship. band?.keys = keys keys?.band = band // Clean up. print("Removing band ...") band = nil print("Removing keys ...") keys = nil Removing band ... Removing keys ... Memory Leaks @pxtrick Ou t p u t :

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var band strong strong strong var keys strong keys: band band: keys Memory Leaks @pxtrick

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var band strong strong var keys strong keys: band band: keys Memory Leaks @pxtrick

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var band strong strong var keys keys: band band: keys Memory Leaks @pxtrick

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// A rockin’ band. class RockBand { var keys: Keyboard? deinit { print("[RockBand] - deinit()") } } // A tasty delight. class Keyboard { weak var band: RockBand? deinit { print("[Keyboard] - deinit()") } } Memory Leaks @pxtrick

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var band strong strong var keys strong keys: band band: keys Memory Leaks @pxtrick weak

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var band strong var keys strong keys: band band: keys Memory Leaks @pxtrick weak

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var band var keys strong keys: band band: keys Memory Leaks @pxtrick

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var band var keys keys: band band: keys Memory Leaks @pxtrick

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var band var keys keys: band band: keys Memory Leaks @pxtrick

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// Create our band. var band: RockBand? = RockBand() // Create our keys. var keys: Keyboard? = Keyboard() // Establish a beautiful friendship. band?.keys = keys keys?.band = band // Clean up. print("Removing band ...") band = nil print("Removing keys ...") keys = nil Removing band ... [RockBand] - deinit() Removing keys ... [Keyboard] - deinit() Memory Leaks @pxtrick Ou t p u t :

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// A rock show. class Concert { var fans: Audience? deinit { print("[Concert] - deinit()") } } // The fans. class Audience { var concert: Concert init(_ concert: Concert) { self.concert = concert } deinit { print("[Audience] - deinit()") } } Memory Leaks @pxtrick

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// Create our rock show. var rockShow: Concert? = Concert() // Create and assign our fans. rockShow?.fans = Audience(rockShow!) // Clean up. print("Removing rockShow...") rockShow = nil Removing rockShow ... Memory Leaks @pxtrick Ou t p u t :

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var rockShow fans: rockShow concert: audience strong strong strong Memory Leaks @pxtrick

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var rockShow strong strong fans: rockShow concert: audience Memory Leaks @pxtrick

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// A rock show. class Concert { var fans: Audience? deinit { print("[Concert] - deinit()") } } // The fans. class Audience { unowned var concert: Concert init(_ concert: Concert) { self.concert = concert } deinit { print("[Audience] - deinit()") } } Memory Leaks @pxtrick

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var rockShow fans: rockShow concert: audience strong strong Memory Leaks @pxtrick unowned

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var rockShow fans: rockShow concert: audience strong Memory Leaks @pxtrick unowned