Swift 3 : Class and Structure

군산대학교 컴퓨터정보통신공학부 컴퓨터정보공학전공

남 광 우

kwnam@kunsan.ac.kr

Swift 3 Tour and Language Guide by Apple꼼꼼한재은씨의 Swift 2 프로그래밍

Class와 Structure

•공통점• Properties : 값을저장하기위한 Properties• Method : 함수기능을제공하기위한메소드• Subscript : 속성값에접근하기위한 subscript • Initializer : 초기상태를설정하기위한초기화• Extension : 디폴트구현이상으로확장• 표준기능을제공하기위한프로토콜

struct Resolution {var width = 0var height = 0

}

class VideoMode {var resolution = Resolution()var interlaced = falsevar frameRate = 0.0var name: String?

}

structure class

Camel 표기법 : • Structure와 class 이름은대문자로시작

• 변수는소문자로시작• 이후단어첫글자대문자

• Class가추가적으로갖는기능• 상속기능• Type Casting 기능• Deinitializer기능(소멸자)• 하나이상의레퍼런스카운팅   

•값의전달• Structure : Value Type• Class : Reference Type

Class와 Structure

Class와 Structure

• Method와 Properties

• Instance 생성

struct Resolution {var width = 0var height = 0

func desc() ‐> String {return “Resolution 구조체”;

}}

class VideoMode {var resolution = Resolution()var interlaced = falsevar frameRate = 0.0var name: String?

func desc() ‐> String {return “Resolution 구조체”;

}}

structure class

let  someResolution = Resolution(); let  someVideo = VideoMode();

Properties 접근

• Propertie 접근방법(structure)

• Propertie 접근방법(Class)

let  someResolution = Resolution();

let  someVideo = VideoMode();

print("The width of someResolution is \(someResolution.width)")// Prints "The width of someResolution is 0

someVideoMode.resolution.width = 1280print("The width of someVideoMode is \(someVideo.resolution.width)")// Prints "The width of someVideoMode is 0"

Memberwise 초기화

• Structure만지원• Properties 들을별도구현없이생성자형태로초기화가능

• 다음두가지형태모두지원

• 예

let vga = Resolution(width: 640, height: 480)

Resoultion();Resolution( width: int, height : int ); 

Structure = Value Type• Structure는 Value Type

let  hd = Resolution(width: 1920, height: 1080)var cinema = hd

cinema.width = 2048

print("cinema is now \(cinema.width) pixels wide")

print("hd is still \(hd.width) pixels wide") Result : 1920

Result : 2048

Structure = Reference Type

let  tenEighty = VideoMode()tenEighty.resolution = hdtenEighty.interlaced = truetenEighty.name = "1080i"tenEighty.frameRate = 25.0

• Structure는 Reference Type

let  alsoTenEighty = tenEightyalsoTenEighty.frameRate = 30.0

print("The frameRate is now \(tenEighty.frameRate)")Result : 30.0

print("The frameRate is now \(alsoTenEighty.frameRate)")

Result : 30.0

동일 비교

• === 와 !==• Identical to (===)• Not identical to (!==)

let  hdtv01 = VideoMode();let   hdtv02 = tenEighty;

let   hdtv03 = VideoMode();

if  ( hdtv01 === hdtv02 ) {print(“ hdtv01 === hdtv02 “);

}

if(  (hdtv01 === hdtv03 ) }print(“ hdtv01 === hdtv03 “);

}

true

false

Structure와 Class 선택

•다음의경우중하나이상해당하면 Structure

• 서로연관된몇개의기본데이터타입을캡슐화

• 상속필요없음

• 값의전달에 Value Type이합리적일때

• 캡슐화된원본데이터를보존해야할때

Properties• Stored Properties

• Computed Properties

• Type Properties

struct FixedLengthRange {var firstValue: Intlet length: Int

}

struct Rect {var origin = Point()var center: Point {get {let centerX = origin.x + (size.width / 2)let centerY = origin.y + (size.height / 2)return Point(x: centerX, y: centerY)

}}

}

struct SomeStructure {static var storedTypeProperty = "Some value."static var computedTypeProperty: Int {return 1

}}

Stored Properties•변수형 Stored Properties

•상수형 Stored Propties

struct FixedLengthRange {var firstValue: Intlet length: Int

}var rangeOfThreeItems = FixedLengthRange(firstValue: 0, length: 3)rangeOfThreeItems.firstValue = 6

let rangeOfFourItems = FixedLengthRange(firstValue: 0, length: 4)// this range represents integer values 0, 1, 2, and 3

rangeOfFourItems.firstValue = 6  // Error !!!

Stored Properties• Lazy Stored Properties

class DataImporter {var fileName = "data.txt"

}

class DataManager {lazy var importer = DataImporter()var data = [String]()

}

let manager = DataManager()manager.data.append("Some data")manager.data.append("Some more data")// the DataImporter instance는아직생성되지않음

print(manager.importer.fileName)// 실제사용되는순간 DataImporter인스턴스가생성됨

Computed Properties•연산 Properties

• 실제값을저장하는것이아니라, 값을만들기위한메소드를저장

struct Point {var x = 0.0, y = 0.0

}struct Size {var width = 0.0, height = 0.0

}

struct Rect {var origin = Point()var size = Size()var center: Point {get {let centerX = origin.x + (size.width / 2)let centerY = origin.y + (size.height / 2)return Point(x: centerX, y: centerY)

}set(newCenter) {origin.x = newCenter.x ‐ (size.width / 2)origin.y = newCenter.y ‐ (size.height / 2)

}}

}

var square = Rect(origin: Point(x: 0.0, y: 0.0), size: Size(width: 10.0, height: 10.0))

let initialSquareCenter = square.center

square.center = Point(x: 15.0, y: 15.0)

print("square.origin is now at (\(square.origin.x), \(square.origin.y))")// Prints "square.origin is now at (10.0, 10.0)"

Computed Properties•연산 Properties의사용

Computed Properties•연산 Properties에서 setter파라미터생략

struct Rect {var origin = Point()var size = Size()var center: Point {get {let centerX = origin.x + (size.width / 2)let centerY = origin.y + (size.height / 2)return Point(x: centerX, y: centerY)

}set {

origin.x = newValue.x ‐ (size.width / 2)origin.y = newValue.y ‐ (size.height / 2)

}set (newCenter) {origin.x = newCenter.x ‐ (size.width / 2)origin.y = newCenter.y ‐ (size.height / 2)

}

}}

Property Observer• Properties 값의변경을감지

• willSet : 값이저장되기직전호출• didSet : 값이저장된직후호출

class StepCounter {var totalSteps: Int = 0 {willSet(newTotalSteps) {print("About to set totalSteps to \(newTotalSteps)")

}didSet {if totalSteps > oldValue {print("Added \(totalSteps ‐ oldValue) steps")

}}

}}

let stepCounter = StepCounter()stepCounter.totalSteps = 200// About to set totalSteps to 200// Added 200 stepsstepCounter.totalSteps = 360// About to set totalSteps to 360// Added 160 steps

Type Properties•정의

• 같은 Type의모든인스턴스가공유하는 Properties

struct SomeStructure {static var storedTypeProperty = "Some value."static var computedTypeProperty: Int {return 1

}}enum SomeEnumeration {static var storedTypeProperty = "Some value."static var computedTypeProperty: Int {return 6

}}class SomeClass {static var storedTypeProperty = "Some value."static var computedTypeProperty: Int {return 27

}class var overrideableComputedTypeProperty: Int {return 107

}}

struct AudioChannel {static let thresholdLevel = 10static var maxInputLevelForAllChannels = 0var currentLevel: Int = 0 {didSet {if currentLevel > AudioChannel.thresholdLevel {// cap the new audio level to the threshold levelcurrentLevel = AudioChannel.thresholdLevel

}if currentLevel > AudioChannel.maxInputLevelForAllChannels {// store this as the new overall maximum input levelAudioChannel.maxInputLevelForAllChannels = currentLevel

}}

}}

Type Properties• Type Properties의사용예

Method• Instance Method

• 특정 Class나 structure의인스턴스에속하는함수

class Counter {var count = 0func increment() {count += 1

}func increment(by amount: Int) {count += amount

}func reset() {count = 0

}}

let counter = Counter()// 0counter.increment()// 1

counter.increment(by: 5)// 6

counter.reset()// 0

Method• self

• class 나 structure 내의 property를참조할때

func increment() {self.count += 1

}struct Point {var x = 0.0, y = 0.0func isToTheRightOf(x: Double) ‐> Bool {return self.x > x

}}let somePoint = Point(x: 4.0, y: 5.0)if somePoint.isToTheRightOf(x: 1.0) {print("This point is to the right of the line where x == 1.0")

}

Method• mutating

• 인스턴스메소드내에서 Property를수정하는함수

struct Point {var x = 0.0, y = 0.0mutating func moveBy(x deltaX: Double, y deltaY: Double) {x += deltaXy += deltaY

}}

var somePoint = Point(x: 1.0, y: 1.0)somePoint.moveBy(x: 2.0, y: 3.0)

print("The point is now at (\(somePoint.x), \(somePoint.y))")// Prints "The point is now at (3.0, 4.0)"

Method• self에값을할당하기

• mutating 메소드내에서실행

struct Point {var x = 0.0, y = 0.0mutating func moveBy(x deltaX: Double, y deltaY: Double) {self = Point(x: x + deltaX, y: y + deltaY)

}}

Method• enumeration에서 self에값을할당하기

enum TriStateSwitch {case off, low, highmutating func next() {switch self {case .off:self = .low

case .low:self = .high

case .high:self = .off

}}

}var ovenLight = TriStateSwitch.lowovenLight.next()// ovenLight is now equal to .highovenLight.next()// ovenLight is now equal to .off

Type Method•정의

• 인스턴스를생성하지않고호출할수있는메소드• 예 : Java의 static method

• class keyword 사용

•주의• class에서는 class, struct/enum에서는 static키워드• 인스턴스메소드를참조할수없음

class SomeClass {class func someTypeMethod() {// type method implementation goes here

}}

SomeClass.someTypeMethod()

struct LevelTracker {static var highestUnlockedLevel = 1var currentLevel = 1

static func unlock(_ level: Int) {if level > highestUnlockedLevel { highestUnlockedLevel = level }

}

static func isUnlocked(_ level: Int) ‐> Bool {return level <= highestUnlockedLevel

}

@discardableResultmutating func advance(to level: Int) ‐> Bool {if LevelTracker.isUnlocked(level) {currentLevel = levelreturn true

} else {return false

}}

}

class Player {var tracker = LevelTracker()let playerName: Stringfunc complete(level: Int) {LevelTracker.unlock(level + 1)tracker.advance(to: level + 1)

}init(name: String) {playerName = name

}}

var player = Player(name: "Argyrios")player.complete(level: 1)print("highest unlocked level is now \(LevelTracker.highestUnlockedLevel)")

player = Player(name: "Beto")if player.tracker.advance(to: 6) {print("player is now on level 6")

}

Type Method

상속(Inheritance)

•기본클래스의정의

•인스턴스생성과사용

class Vehicle {var currentSpeed = 0.0var description: String {return "traveling at \(currentSpeed) miles per hour"

}func makeNoise() {// do nothing ‐ an arbitrary vehicle doesn't necessarily make a noise

}}

let someVehicle = Vehicle()

print("Vehicle: \(someVehicle.description)")// Vehicle: traveling at 0.0 miles per hour

상속(Inheritance)

•상속의구현

•상속인스턴스생성과사용

class Bicycle: Vehicle {var hasBasket = false

}

let bicycle = Bicycle()bicycle.hasBasket = truebicycle.currentSpeed = 15.0

print("Bicycle: \(bicycle.description)")// Bicycle: traveling at 15.0 miles per hour

상속(Inheritance)

class Tandem: Bicycle {var currentNumberOfPassengers = 0

}

let tandem = Tandem()tandem.hasBasket = truetandem.currentNumberOfPassengers = 2tandem.currentSpeed = 22.0

print("Tandem: \(tandem.description)")// Tandem: traveling at 22.0 miles per hour

•상속의사용

Overriding

class Train: Vehicle {override func makeNoise() {print(＂Choo Choo＂)

}}

•메소드의 Overriding

•사용예

let train = Train()train.makeNoise()// Prints "Choo Choo"

Overriding Getter/Setter

class Car: Vehicle {var gear = 1override var description: String {return super.description + " in gear \(gear)"

}}

• getter의 Overriding

•사용

let car = Car()car.currentSpeed = 25.0car.gear = 3print("Car: \(car.description)")// Car: traveling at 25.0 miles per hour in gear 3

Overriding Observer

• Observer의 Overriding

•사용

class AutomaticCar: Car {override var currentSpeed: Double {didSet {gear = Int(currentSpeed / 10.0) + 1

}}

}

let automatic = AutomaticCar()automatic.currentSpeed = 35.0print("AutomaticCar: \(automatic.description)")

Preventing Override

• final• final var• final func• final class func• final subscript