Sawijining closure nangkep (capture) variabel sing dirujuk, lan njaga variabel kasebut tetep urip. Nalika closure nangkep self lan self uga nyekel closure kasebut (minangka stored property), loro-lorone padha njaga tetep urip ing selawase — yaiku sing mbocorake memori. Sawijining kaya bakal mecah cycle kasebut.
[weak self]ARC mbebasake sawijining objek nalika reference count-e tekan nol. Capture sing strong bakal nambah count kasebut.
final class Downloader {
var onDone: (() -> Void)? // stored closure -> strong
func start() {
// BAD: closure captures self strongly, self holds closure -> cycle
onDone = { self.cleanup() }
// GOOD: weak capture, self can deallocate
onDone = { [weak self] in
guard let self else { return } // safely unwrap; bail if gone
self.cleanup()
}
}
func cleanup() {}
}
[weak self] — self dadi optional; bakal nil yen objek wis dibebasake. Standar sing aman nalika objek bisa uga urip luwih suwe tinimbang closure.[unowned self] — dudu optional, ora ana overhead ARC, nanging bakal crash yen self wis ora ana. Gunakake mung nalika self dijamin urip luwih suwe tinimbang closure.Task { [weak self] in
let data = await self?.fetch() // self? short-circuits if deallocated
}
Closure non-escaping (contone map, filter, forEach) mlaku kanthi sinkron lan langsung ngeculake capture — ora ana cycle, ora butuh [weak self]. Risikone ana ing closure escaping lan stored: completion handler, Timer, NotificationCenter, Combine sink, lan blok delegate.
Retain cycle iku memory leak sing paling umum ing iOS, lan ora katon nganti Instruments nuduhake memori sing terus mundhak. Ngerti persis kapan closure escape lan kenapa [weak self] dibutuhake — tinimbang nganggo iku kanthi refleks ing endi-endi — mbedakake engineer sing ngerti ARC saka sing mung melu-melu wae.
Pustaka pitakon wawancara IT kanthi jawaban rinci — saka Junior nganti Senior.
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