ca.swift_2.pdf - Speaker Deck

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RxSwift Operators Tips 2017/03/1 CA.swift

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About Me ҏ౻ɹګฏ Github : KyoheiG3 Twitter : @KyoheiG3

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͖Ε͍ͳ઒ͷྲྀΕΛकΔͨΊͷ੍໿ͦͷᶃ ઒Λ෼அ͠ͳ͍

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͖Ε͍ͳ઒ͷྲྀΕΛकΔͨΊͷ੍໿ͦͷᶃ → DisposeBagΛෳ਺ʹ෼͚ͳ͍

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flatMap

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flatMap Observable͔Βૹ৴͞ΕͨΞΠςϜΛObservablesʹม׵͠ɺ ͦͷޙͦΕΒ͔Βૹ৴͞ΕΔΞΠςϜΛ̍ͭͷObservable΁ม ׵͢Δɻ

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flatMap ઒͔Β઒΁ɺྲྀΕΛͭͳ͙

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Bad Stream botton.rx.tap .subscribe(onNext: { URLSession.shared.rx.json(request: request) .subscribe(onNext: { ... }) .addDisposableTo(disposeBag) }) .addDisposableTo(disposeBag)

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Good Stream botton.rx.tap .flatMap { URLSession.shared.rx.json(request: request) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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flatMapͷಛ௃ લճͷΠϕϯτ͕ऴ͍ྃͯ͠ͳͯ͘΋ΞΠςϜ͕ετϦʔϜʹྲྀ ΕΔͷͰɺಉ͡ॲཧ͕ෳ਺ճߦΘΕΔՄೳੑ͕͋Δɻ

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ඇಉظॲཧͰ΍Γ͍ͨ͜ͱ ௨৴ͳͲͷඇಉظॲཧ͸ɺॲཧத͸ετϦʔϜΛྲྀ͞ͳ͍ɺ· ͨ͸࠷৽ͷετϦʔϜ͚ͩΛྲྀ͍ͨ͠ɻ

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flatMapLatest

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flatMapLatest ઒ͷྲྀΕΛஅͪ੾ͬͯɺ࣍ͷ઒΁ͱྲྀΕΛͭͳ͙

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Bad Stream botton.rx.tap .subscribe(onNext: { requestDisposeBag = DisposeBag() URLSession.shared.rx.json(request: request) .subscribe(onNext: { ... }) .addDisposableTo(requestDisposeBag) }) .addDisposableTo(disposeBag)

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Good Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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flatMapLatestͷಛ௃ ৽͍͠Πϕϯτ͕ىͬͨ͜ΒલͷΠϕϯτΛഁغͯ࣍͠ͷΠϕϯ τΛߦ͏ͷͰɺ୯Ұͷॲཧ͔͠ߦΘΕͳ͍ɻ Timer΍IntervalͳͲͷඇಉظॲཧ΋ɺflatMapLatestͱ૬ੑ͕ Α͍ɻ

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Timer Stream botton.rx.tap .flatMapLatest { Observable.timer(1, scheduler: scheduler) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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debounceͱॲཧ͕Α͘ࣅ͍ͯΔ

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Debounce botton.rx.tap .debounce(1, scheduler: scheduler) .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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DebounceͱTimer Streamͷҧ͍ ετϦʔϜʹྲྀΕ͖ͯͨ஋Λ΋ͱʹintervalΛม͑Δ͜ͱ͕Ͱ ͖Δɻ

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έʔεͦͷᶃ ΞΠςϜΛड͚औ͔ͬͯΒɺҰఆ࣌ؒޙʹΞΠςϜΛετϦʔϜ ʹྲྀ͍ͨ͠ɻ஗Ԇ࣌ؒ͸ΞΠςϜͷ಺༰ʹΑͬͯ൑அ͢Δɻ

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{ "num": 10, "title": "Timer Stream" }

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Timer Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .flatMapLatest { json -> Observable in Observable.timer(json["num"] as! Int, scheduler: scheduler) .map { _ in json } } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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έʔεͦͷᶄ ΞΠςϜΛड͚औͬͨΒετϦʔϜʹྲྀ͕͢ɺҰఆ࣌ؒޙʹnil ΛετϦʔϜʹྲྀ͍ͨ͠ɻ஗Ԇ࣌ؒ͸ΞΠςϜͷ಺༰ʹΑͬͯ ൑அ͢Δɻ

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έʔεͦͷᶄ startWithΛ࢖͏

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Timer Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .flatMapLatest { json -> Observable in Observable.timer(json["num"] as! Int, scheduler: scheduler) .map { _ in nil } .startWith(json) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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flatMapFirst

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flatMapFirst ઒ͷྲྀΕ͕ࢭ·Δ·Ͱɺ࣍ͷ઒΁͸ͭͳ͕ͳ͍

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Bad Stream var requesting = false botton.rx.tap .subscribe(onNext: { if requesting { return } requesting = true requestDisposeBag = DisposeBag() URLSession.shared.rx.json(request: request) .subscribe(onNext: { requesting = false }) .addDisposableTo(requestDisposeBag) }) .addDisposableTo(disposeBag)

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Good Stream botton.rx.tap .flatMapFirst { URLSession.shared.rx.json(request: request) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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flatMapFirstͷಛ௃ ࠷ॳʹૹ৴͞ΕͨΞΠςϜͷॲཧ͕׬ྃ͢Δ·Ͱ͸ɺͦͷޙʹ ૹΒΕͨΞΠςϜΛ఻ൖ͠ͳ͍ͷͰɺ୯Ұͷॲཧ͔͠ߦΘΕͳ ͍ɻ

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Timer Stream botton.rx.tap .flatMapFirst { Observable.timer(1, scheduler: scheduler) } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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throttleͱॲཧ͕Α͘ࣅ͍ͯΔ

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Throttle botton.rx.tap .throttle(1, scheduler: scheduler) .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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Throttleͷ஫ҙ఺ throttle͸ετϦʔϜ1ൃ໨ͷΞΠςϜ͕ྲྀΕͯ͘ΔͬΆ͍ɻ ੲ͸ྲྀΕͯ͜ͳ͔ͬͨͷͰɺ΋͔ͨ͠͠ΒόʔδϣϯʹΑͬͯ มΘΔ͔΋ɻ

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͖Ε͍ͳ઒ͷྲྀΕΛकΔͨΊͷ੍໿ͦͷᶄ ઒ʹ΋ͷΛ౤͛ೖΕͳ͍

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͖Ε͍ͳ઒ͷྲྀΕΛकΔͨΊͷ੍໿ͦͷᶄ → ΫϩʔδϟͰselfΛࢀরͤ͞ͳ͍

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selfΛࢀরͤ͞ͳ͍ํ๏ ෳ਺ͷετϦʔϜΛ߹੒ɺ͋Δ͍͸ঢ়ଶΛ஌Δඞཁ͕͋Δɻ RxͷoperatorsҰཡͳͲΛ֬ೝͯ͠Έͯɺ(x, y)Έ͍ͨʹ2ͭͷ ஋Λࢀর͍ͯ͠ΔΑ͏ͳoperator͸߹੒νϟϯεɻ ׬શʹࢀর͠ͳ͍ͷ͸೉͍͠ͷͰɺͰ͖ΔݶΓͰ΍ͬͯΈΔɻ

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withLatestFrom

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withLatestFrom ͋ΔετϦʔϜʹରͯ͠ɺผͷετϦʔϜͷ࠷৽ͷΞΠςϜΛ߹ ੒͢Δɻ

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Bad Stream let other = Variable(0) botton.rx.tap .subscribe(onNext: { [weak self] in self?.other.asObservable() .subscribe(onNext: { ... }) .addDisposableTo(disposeBag) }) .addDisposableTo(disposeBag)

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Self Reference let other = Variable(0) botton.rx.tap .subscribe(onNext: { [weak self] in print(self?.other.value) }) .addDisposableTo(disposeBag)

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Good Stream let other = Variable(0) botton.rx.tap .withLatestFrom(other.asObservable()) .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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withLatestFromͷಛ௃ subscribeޙʹετϦʔϜʹྲྀΕͨ࠷৽ͷΞΠςϜͰ͋Ε͹ɺ VariableͷΑ͏ʹ஋Λอ͍࣋ͯ͠ͳͯ͘΋͍֮͑ͯͯ͘ΕΔͷ Ͱ߹੒͢Δ͜ͱ͕Ͱ͖Δɻ

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Good Stream let other = PublishSubject() botton.rx.tap .withLatestFrom(other) .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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scan

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scan Observable͔Βૹ৴͞ΕΔΞΠςϜʹ࿈ଓͯؔ͠਺Λద༻͢ Δɻ

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Bad Stream let some = Variable(0) botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { [weak self] json in let num = json["num"] as! Int if let value = self?.some.value { let new = value + num self?.some.value = new return new } return 0 } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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Good Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { json in json["num"] as! Int } .scan(0) { some, new in some + new } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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scanͷಛ௃ scanΛߦ͏͜ͱͰɺ͋ΔετϦʔϜʹରͯ͠ผͷΞΠςϜΛྲྀ ͢͜ͱ͕Ͱ͖Δɻ ετϦʔϜʹྲྀͨ͠ΞΠςϜ͸อ࣋͞Ε͍ͯΔͷͰɺ࣍ճετ ϦʔϜʹΞΠςϜ͕ྲྀΕ͖ͯͨࡍʹɺอ͍࣋ͯ͠ΔΞΠςϜͱ ྲྀΕ͖ͯͨΞΠςϜͷ྆ํΛಘΔ͜ͱ͕Մೳɻ

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scanͷಛ௃ ৚݅ʹ߹Θͳ͚Ε͹ಉҰͷΞΠςϜΛྲྀ͠ଓ͚ͯɺ distinctUntilChangedΛ࣮ߦͯ͠ॲཧΛল͘͜ͱ΋Ͱ͖Δɻ

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Good Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { json in json["num"] as! Int } .scan(0) { some, new in new > some ? new : some } .distinctUntilChanged() .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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scanͷಛ௃ อ͍࣋ͯ͠ΔΞΠςϜ͕มΘΔࡍʹɺݹ͍ΞΠςϜΛར༻ͯ͠ॲ ཧΛߦ͏Α͏ͳ͜ͱ΋Մೳɻ

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Good Stream botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { json in json["num"] as! Int } .scan(0) { some, new in if new > some { ... return new } return some } .distinctUntilChanged() .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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distinctUntilChanged

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distinctUntilChanged ॏෳͨ͠ΞΠςϜͷ৔߹͸ૹ৴͠ͳ͍Α͏ʹ͢ΔΦϖϨʔλɻ

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distinctUntilChanged botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { json in json["num"] as! Int } .distinctUntilChanged() .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)

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distinctUntilChangedͷಛ௃ ΞΠςϜ͕EquatableͰ͸ͳ͍৔߹͸ΫϩʔδϟΛड͚औͬͯͦ ͷΫϩʔδϟΛ࣮ߦ͠ɺ໭Γ஋͕trueͷ͏ͪ͸ॲཧΛܧଓ͠ͳ ͍Α͏ͳৼΔ෣͍Λ͍ͯ͠Δɻ

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distinctUntilChangedͷಛ௃ ετϦʔϜʹྲྀΕͨΞΠςϜΛอ͓͖࣋ͯ͠ɺ࣍ճετϦʔϜʹ ΞΠςϜ͕ྲྀΕ͖ͯͨࡍʹ৽چ྆ํͷΞΠςϜΛಘΔ͜ͱ͕Մ ೳɻ ॳظ஋Λؾʹ͠ͳ͍ͷͰ͋Ε͹ɺscanͱಉ͡Α͏ͳॲཧΛ΋͏ গ͠୹͘ॻ͘͜ͱ΋Ͱ͖Δɻ

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distinctUntilChanged botton.rx.tap .flatMapLatest { URLSession.shared.rx.json(request: request) } .map { json in json["num"] as! Int } .distinctUntilChanged { old, new in if (new <= old) == false { ... } return new <= old } .subscribe(onNext: { ... }) .addDisposableTo(disposeBag)