Enumerations - The Swift Programming Language (Swift 5.6)
defines a common type for a group of related values and enables you to work with those values in a type-safe way
⇒ 관련된 값 묶을 때 사용 → type-safe
switch directionToHead {
case .north:
print("Lots of planets have a north")
case .south:
print("Watch out for penguins")
case .east:
print("Where the sun rises")
case .west:
print("Where the skies are blue")
}
iterating over enum case
← :CaseIterable
프로토콜로 case 반복 접근 가능
enum Beverage: CaseIterable {
case coffee, tea, juice
}
let numberOfChoices = Beverage.allCases.count
print("\(numberOfChoices) beverages available")
// Prints "3 beverages available"
for beverage in Beverage.allCases {
print(beverage)
}
// coffee
// tea
// juice
enum Barcode {
case upc(Int, Int, Int, Int)
case qrCode(String)
}
var productBarcode = Barcode.upc(8, 85909, 51226, 3)
productBarcode = .qrCode("ABCDEFGHIJKLMNOP")
switch productBarcode {
case .upc(let numberSystem, let manufacturer, let product, let check):
print("UPC: \(numberSystem), \(manufacturer), \(product), \(check).")
case .qrCode(let productCode):
print("QR code: \(productCode).")
}
// Prints "QR code: ABCDEFGHIJKLMNOP."
switch productBarcode {
case let .upc(numberSystem, manufacturer, product, check):
print("UPC : \(numberSystem), \(manufacturer), \(product), \(check).")
case let .qrCode(productCode):
print("QR code: \(productCode).")
}
// Prints "QR code: ABCDEFGHIJKLMNOP."
enum Planet: Int {
case mercury = 1, venus, earth, mars, jupiter, saturn, uranus, neptune
}
let earthsOrder = Planet.earth.rawValue
// earthsOrder is 3
enum CompassPoint: String {
case north, south, east, west
}
let sunsetDirection = CompassPoint.west.rawValue
// sunsetDirection is "west"
If you define an enumeration with a raw-value type, the enumeration automatically receives an initializer that takes a value of the raw value’s type (as a parameter called
rawValue
) and returns either an enumeration case ornil
.
⇒ init과 rawValue를 사용한 enum 생성은 옵셔널 → 해당 case반환 또는 (없는 경우) nil
let positionToFind = 11
if let somePlanet = Planet(rawValue: positionToFind) {
switch somePlanet {
case .earth:
print("Mostly harmless")
default:
print("Not a safe place for humans")
}
} else {
print("There isn't a planet at position \(positionToFind)")
}
// Prints "There isn't a planet at position 11"