Optional wani type ne wanda ko dai yana riƙe da value ko kuma yana riƙe da nil (babu value). Swift yana sanya nil a bayyane a cikin type system: String ba zai taɓa zama nil ba, amma yana iya. Wannan shi ne yadda Swift ke kawar da yawancin null-pointer crashes a lokacin compile.
String?A ƙarƙashin fasali, Int? wani enum ne mai cases guda biyu: .some(value) ko .none. Ba za ka iya amfani da wrapped value kai tsaye ba — dole ne ka fara buɗe shi (unwrap).
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 ɗin ! yana yin force-unwrap: name! yana crash idan name ya zama nil. Yi amfani da shi kawai lokacin da program logic ta tabbatar da value — in ba haka ba, fifita if let, guard let, ko ??.
let url = URL(string: "https://a.com")! // OK: literal is always valid
let user = fetchUser()! // BAD: crashes on nil
String!) suna crash a shiru lokacin da aka shiga su alhali suna nil — abu ne na kowa da @IBOutlet.user?.address?.city yana yin short-circuit zuwa nil maimakon crash.Optionals suna sanya "wannan yana iya rasuwa" a cikin type, don haka compiler ya tilasta maka sarrafa yanayin da babu komai. Masu tambayoyi suna amfani da wannan don ganin ko za ka kai ga guard let da ?? maimakon yayyafa ! ko'ina, wanda shi ne bambanci tsakanin app mai saurin crash da mai aminci.
Ɗakin karatu na tambayoyin hira na IT tare da amsoshi cikakke — daga Junior zuwa Senior.
Ba da Gudummawa