Swift学習ノート自己判断リンク

class Person {
    var residence: Residence?
}

class Residence {
    var rooms = [Room]()
    var numberOfRooms: Int {
        return rooms.count
    }
    subscript(i: Int) -> Room {
        get {
            return rooms[i]
        }
        set {
            rooms[i] = newValue
        }
    }
    func printNumberOfRooms(){
        println("The number of rooms is \(numberOfRooms)")
    }
    var address: Address?
}

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 != nil {
            return buildingName
        } else if buildingNumber != nil {
            return buildingNumber
        } else {
            return nil
        }
    }
}

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.")
}
let someAddress = Address()
someAddress.buildingNumber = "29"
someAddress.street = "Acacia Road"
john.residence?.address = someAddress

if john.residence?.printNumberOfRooms() != nil {
     println("It was possible to print the number of rooms.")
} else {
    println("It was not possible to print the number of rooms.")
}
if (john.residence?.address = someAddress) != nil {
    println("It was possible to set the address.")
} else {
    println("It was not possible to set the address.")
}

if let firstRoomName = john.residence?[0].name {
    println("The first room name is \(firstRoomName).")
} else {
    println("Unable to retrieve the first room name.")
}

自己判断は非空判断、または賦値判断と理解でき、この判断が賦値に成功すれば成功し、そうでなければ失敗する