Optional iku sawijining tipe sing bisa ngemot nilai utawa ngemot nil (ora ana nilai). Swift ndadekake nil cetha ing sistem tipe: String ora bakal tau bisa nil, nanging String? bisa. Iki carane Swift ngilangi paling akeh crash null-pointer nalika compile time.
Ing njero, Int? iku enum kanthi loro case: .some(value) utawa .none. Sampeyan ora bisa nganggo nilai sing dibungkus kanthi langsung — sampeyan kudu unwrap dhisik.
var name: String? = "Ada" // Optional String, currently .some("Ada")
var missing: String? = nil // .none
// if let: bind only when non-nil, scoped to the block
if let name = name {
print(name.count) // safe: name is a plain String here
}
// guard let: unwrap or exit early — keeps the happy path un-nested
func greet(_ input: String?) {
guard let input else { return } // Swift 5.7 shorthand
print("Hi \(input)") // input is non-optional below
}
// nil-coalescing: supply a default
let display = name ?? "Anonymous"
Operator ! nindakake force-unwrap: name! bakal crash yen name iku nil. Gunakake iki mung nalika sawijining nilai wis dijamin dening logika program — yen ora, luwih becik nganggo if let, guard let, utawa ??.
let url = URL(string: "https://a.com")! // OK: literal is always valid
let user = fetchUser()! // BAD: crashes on nil
String!) crash tanpa swara nalika diakses pas isih nil — kerep kedadeyan karo @IBOutlet.user?.address?.city bakal short-circuit dadi nil tinimbang crash.Optionals nyandhi "iki bisa uga ora ana" ing tipe, mula compiler meksa sampeyan nangani kasus kosong. Pewawancara nganggo iki kanggo ndeleng apa sampeyan milih guard let lan ?? tinimbang nyebar ! ing endi-endi, sing dadi bedane antarane app sing gampang crash lan app sing aman.
Pustaka pitakon wawancara IT kanthi jawaban rinci — saka Junior nganti Senior.
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