Closure yana capture variables ɗin da yake magana a kansu, yana kiyaye su da rai. Lokacin da closure ya capture self kuma self yana riƙe closure ɗin (a matsayin stored property), suna kiyaye juna da rai har abada — wani da ke zubar da memory. Wani kamar yana karya wannan cycle.
[weak self]ARC yana 'yantar da object lokacin da reference count ɗinsa ya kai sifili. Strong capture yana ƙara wannan ƙidaya.
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 ya zama optional; yana nil idan an 'yantar da object. Aminci na tsohuwa lokacin da object na iya rayuwa fiye da closure.[unowned self] — ba optional ba, babu ARC overhead, amma yana crash idan self ya riga ya tafi. Yi amfani da shi kawai lokacin da an tabbatar self zai rayu fiye da closure.Task { [weak self] in
let data = await self?.fetch() // self? short-circuits if deallocated
}
Non-escaping closures (misali map, filter, forEach) suna gudana a synchronously kuma suna 'yantar da captures nan take — babu cycle, babu bukatar [weak self]. Haɗarin yana tare da escaping, stored closures: completion handlers, Timer, NotificationCenter, Combine sinks, delegate blocks.
Retain cycles su ne memory leak da suka fi zama gama-gari a iOS, kuma ba a ganin su har sai Instruments ya nuna memory mai girma. Sanin daidai lokacin da closure ke escape da dalilin da ake bukatar [weak self] — sabanin kai ga shi ba tunani ko'ina — shi ne bambanci tsakanin injiniyoyin da suka fahimci ARC da waɗanda ke bin shi kamar al'ada.
Ɗakin karatu na tambayoyin hira na IT tare da amsoshi cikakke — daga Junior zuwa Senior.
Ba da Gudummawa