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1. swift 0x12
optional chaining
문현진(arnold@css99.co.kr)
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서 “마메스"를 검색하세요.

2. 옵셔널 체인
옵셔널 값이 nil인가요?

3. forced unwrapping
class Person {
var residence: Residence?
}
class Residence {
var numberOfRooms = 1
}
let john = Person()
let roomCount = john.residence.numberOfRooms

4. forced unwrapping
class Person {
var residence: Residence?
}
class Residence {
var numberOfRooms = 1
}
let john = Person()
let roomCount = john.residence.numberOfRooms
Runtime Error

5. forced unwrapping
nil인지 물어본다. (john.residence == nil)
if let roomCount = john.residence?.numberOfRooms {
println("John's residence has (roomCount) room(s).")
} else {
println("Unable to retrieve the number of rooms.")
}
// prints "Unable to retrieve the number of rooms."

6. forced unwrapping
nil인지 물어본다. (john.residence != nil)
john.residence = Residence()
if let roomCount = john.residence?.numberOfRooms {
println("John's residence has (roomCount) room(s).")
} else {
println("Unable to retrieve the number of rooms.")
}
// prints "Unable to retrieve the number of rooms."

7. 옵셔널 체인을 위한 모델 클래스 선언
class Person {
var residence: Residence?
}
class Residence {
var rooms = Room[]()
var numberOfRooms: Int {
return rooms.count
}
subscript(i: Int) -> Room {
return rooms[i]
}
func printNumberOfRooms() {
println("The number of rooms is
(numberOfRooms)")
}
var address: Address?
}

8. 옵셔널 체인을 위한 모델 클래스 선언
class Room {
let name: String
init(name: String) { self.name = name
}
}
class Address {
var buildingName: String?
var buildingNumber: String?
var street: String?
func buildingIdentifier() -> String? {
if buildingName {
return buildingName
} else if buildingNumber {
return buildingNumber
} else {
return nil
}
}
}

9. 옵셔널 체인을 통한 프로퍼티 호출
let john = Person()
if let roomCount = john.residence?.numberOfRooms {
println("John's residence has (roomCount) room(s).")
} else {
println("Unable to retrieve the number of rooms.")
}
// prints "Unable to retrieve the number of rooms."

10. 옵셔널 체인을 통한 메소드 호출
func printNumberOfRooms() {
println("The number of rooms is (numberOfRooms)")
}
if john.residence?.printNumberOfRooms() {
println("It was possible to print the number of rooms.")
} else {
println("It was not possible to print the number of rooms.")
}
// prints "It was not possible to print the number of rooms."

11. 옵셔널 체인을 통한 서브스크립트 호출
if let firstRoomName = john.residence?[0].name {
println("The first room name is (firstRoomName).")
} else {
println("Unable to retrieve the first room name.")
}
// prints "Unable to retrieve the first room name."

12. 옵셔널 체인을 통한 서브스크립트 호출
let johnsHouse = Residence()
johnsHouse.rooms += Room(name: "Living Room")
johnsHouse.rooms += Room(name: "Kitchen")
john.residence = johnsHouse
if let firstRoomName = john.residence?[0].name {
println("The first room name is (firstRoomName).")
} else {
println("Unable to retrieve the first room name.")
}
// prints "The first room name is Living Room."

13. 여러 단계의 체인 연결
if let johnsStreet = john.residence?.address?.street {
println("John's street name is (johnsStreet).")
} else {
println("Unable to retrieve the address.")
}
// prints "Unable to retrieve the address."

14. 여러 단계의 체인 연결
let johnsAddress = Address()
johnsAddress.buildingName = "The Larches"
johnsAddress.street = "Laurel Street"
john.residence!.address = johnsAddress
if let johnsStreet = john.residence?.address?.street {
println("John's street name is (johnsStreet).")
} else {
println("Unable to retrieve the address.")
}
// prints "John's street name is Laurel Street."

15. 옵셔널 반환값을 이용한 메소드 체인
if let buildingIdentifier = john.residence?.address?.buildingIdentifier() {
println("John's building identifier is (buildingIdentifier).")
}
// prints "John's building identifier is The Larches."
if let upper = john.residence?.address?.buildingIdentifier()?.uppercaseString {
println("John's uppercase building identifier is (upper).")
}
// prints "John's uppercase building identifier is THE LARCHES."