日14:Swiftuiの100日-オプション

オプション、NIL合体、チェックポイント9

オプション

var username: String? = nil
var password: String?

if let unwrappedName = username {
    print("We got a user: \(unwrappedName)")
} else {
    print("The optional was empty.")
}

レットアンドガード

var myVar: Int? = 3

if let unwrapped = myVar {
    print("Run if myVar has a value inside")
}

guard let unwrapped = myVar else {
    print("Run if myVar doesn't have a value inside")
}

func printSquare(of number: Int?) {
    guard let number = number else {
        print("Missing input")
        return
    }

    print("\(number) x \(number) is \(number * number)")
}

printSquare(of: nil)
printSquare(of: 2)

ニール合体

let captains = [
    "Enterprise": "Picard",
    "Voyager": "Janeway",
    "Defiant": "Sisko"
]

let new = captains["Serenity"] ?? "N/A"

オプション連鎖

let names = ["Arya", "Bran", "Robb", "Sansa"]

let chosen = names.randomElement()?.uppercased() ?? "No one"
print("Next in line: \(chosen)")

チェックポイント9

ソリューション