Unowned / Weak References with Closure

変数の生存期間を playground を利用しながら確認していきます。

Transcript

1. Naruki Chigira - Timers inc. GitHub: naru-jpn, Twitter: @naruchigi Unowned / Weak References with Closure
2. ม਺ͷੜଘظؒɺؾʹͯ͠·͔͢ʁ
3. Ϋϩʔδϟ಺Ͱอ࣋͞ΕΔม਺ɺ௥͑·͔͢ʁ
4. DispatchQueue.main.async { [weak self] in // ... }
5. Ϋϩʔδϟ಺Ͱʰ ͱΓ͋͑ͣ [weak self] ʱͯ͠·ͤΜ͔ʁ
6. Playground ͰڍಈΛࡉ͔͘ݟͯΈΑ͏ https://gist.github.com/naru-jpn/fa4c39ce2eda8a803358dad75d04058d
7. class Executor { // MARK: Exeute stored procedure let procedure: () -> () init(procedure: @escaping () -> ()) { self.procedure = procedure } func execute() { self.procedure() } // MARK: Static execution static func execute(procedure: () -> ()) { procedure() } } ΫϩʔδϟΛ࣮ߦ͢ΔΫϥε Executor
8. class Object { var child: Object? weak var weakChild: Object? var closure: (() -> ())? weak var currentExecutor: Executor? } ؍ଌ༻Ϋϥε Object
9. weak var weakObject: Object? = nil // スコープ内外での挙動を見るために if 文でネストさせる // object が解放されていれば weakObject の中身は nil になる if true { let object: Object = Object() weakObject = object print(“\(weakObject)") // nil or not nil? } print(“\(weakObject)") // nil or not nil? ม਺͕ղ์͞Ε͍ͯΔ͔Ͳ͏͔ͷ֬ೝ
10. object object if true { let object: Object = Object() weakObject = object // 1 } // 2 1. ม਺͸είʔϓΛൈ͚ͨΒղ์͞ΕΔ
11. object child object child if true { let object: Object = Object() object.child = object weakObject = object // 1 } // 2 weakObject?.child = nil 2. ࢀরʹΑΔϝϞϦϦʔΫ
12. object child object child if true { let object: Object = Object() object.weakChild = object weakObject = object // 1 } // 2 weakObject?.child = nil 3. weak Λ࢖ͬͯϝϞϦϦʔΫ͠ͳ͍Α͏ʹͨ͠έʔε
13. ॥؀ࢀর͸౰વආ͚·͠ΐ͏
14. object closure object closure if true { let object: Object = Object() object.closure = { print("\(object)") } weakObject = object // 1 } // 2 weakObject?.closure = nil 4. Ϋϩʔδϟ͔ΒͷࢀরʹΑΔϝϞϦϦʔΫ
15. object closure object closure if true { let object: Object = Object() object.closure = { [weak object] in print("\(object)") } weakObject = object // 1 } // 2 5. [weak ---] Λ࢖ͬͯϝϞϦϦʔΫ͠ͳ͍Α͏ʹͨ͠έʔε
16. Ϋϩʔδϟͷ॥؀ࢀরʹ΋஫ҙ
17. object closure object object closure object είʔϓ಺ ؔ਺࣮ߦ࣌ ؔ਺ऴྃ࣌ είʔϓ֎ Executor Executor extension Object { func printWeakSelf() { let executor: Executor = Executor(procedure: { [weak self] in debugPrint("\(self)") }) executor.execute() } } 6. Executor ͷΫϩʔδϟ಺Ͱ [weak self] Λ࢖͏৔߹
18. object closure object object closure object είʔϓ಺ ؔ਺࣮ߦ࣌ ؔ਺ऴྃ࣌ είʔϓ֎ Executor Executor if true { let object: Object = Object() object.printWeakSelf() weakObject = object } 6. Executor ͷΫϩʔδϟ಺Ͱ [weak self] Λ࢖͏৔߹
19. object closure object object closure object Executor Executor είʔϓ಺ ؔ਺࣮ߦ࣌ ؔ਺ऴྃ࣌ είʔϓ֎ extension Object { func printSelf() { let executor: Executor = Executor(procedure: { print("\(self)") }) executor.execute() } } 7. Executor ͷΫϩʔδϟ಺Ͱ [weak self] Λ࢖Θͳ͍৔߹
20. object closure object object closure object Executor Executor είʔϓ಺ ؔ਺࣮ߦ࣌ ؔ਺ऴྃ࣌ είʔϓ֎ if true { let object: Object = Object() object.printSelf() weakObject = object } 7. Executor ͷΫϩʔδϟ಺Ͱ [weak self] Λ࢖Θͳ͍৔߹
21. Ϋϩʔδϟ಺Ͱ self Λࢀরͯ͠΋ϦʔΫ͠ͳ͍৔߹΋͋Δ
22. ඇಉظॲཧ଴ػ࣌ ඇಉظॲཧऴྃ࣌ ؔ਺࣮ߦ࣌ object closure closure Executor object closure Executor extension Object { func printAsynchronousWeakSelf() { let executor: Executor = Executor(procedure: { let time: DispatchTime = .now() + 1.0 DispatchQueue.global().asyncAfter(deadline: time, execute: { [weak self] in print("\(self)") }) }) executor.execute() self.currentExecutor = executor } } 8. ඇಉظॲཧͰ [weak self] Λ࢖͏৔߹
23. ඇಉظॲཧ଴ػ࣌ ඇಉظॲཧऴྃ࣌ ؔ਺࣮ߦ࣌ object closure closure Executor object closure Executor if true { let object: Object = Object() object.printAsynchronousSelf() weakObject = object } sleep(UInt32(3.0)) 8. ඇಉظॲཧͰ [weak self] Λ࢖͏৔߹
24. ඇಉظॲཧ଴ػ࣌ ඇಉظॲཧऴྃ࣌ ؔ਺࣮ߦ࣌ object closure object closure Executor object closure Executor extension Object { func printAsynchronousSelf() { let executor: Executor = Executor(procedure: { DispatchQueue.global().asyncAfter(deadline: .now() + 1.0, execute: { print("\(self)") }) }) executor.execute() self.currentExecutor = executor } } 9. ඇಉظॲཧͰ [weak self] Λ࢖Θͳ͍৔߹
25. ඇಉظॲཧ଴ػ࣌ ඇಉظॲཧऴྃ࣌ ؔ਺࣮ߦ࣌ object closure object closure Executor object closure Executor if true { let object: Object = Object() object.printAsynchronousSelf() weakObject = object } sleep(UInt32(3.0)) 9. ඇಉظॲཧͰ [weak self] Λ࢖Θͳ͍৔߹
26. ඇಉظॲཧͰ͸ίʔϧόοΫ࣌ʹ object ͕ੜଘ͍ͯ͠Δ͔Ͳ͏͔͕มΘͬͯ͘Δ
27. ͨͩ͠ɺϦʔΫ͠ͳ͍͜ͱʹมΘΓ͸ͳ͍
28. ໨తʹԠͯ͡࢖͍෼͚ΒΕΔΑ͏ʹͳΓ͍ͨͰ͢Ͷ
29. ͍͔ͭ [weak self] Λݟͨͱ͖ʹࢥ͍Λ஘ͤͯΈ͍ͯͩ͘͞
35. Motivation / Concept https://developers.google.com/protocol-buffers/ Template message