Swift flatMap 2

Workshop in Fenrir Inc.

1. flatMap ͷ࿩ USAMI Kosuke Fenrir Inc.
2. ͸͡Ίʹ • Swi% ͷ flatMap ʹ͍ͭͯ࿩͠·͢ • flatMap ͦͷ΋ͷ͸͍Ζ͍Ζͳݴޠʹ͋Γ·͢ • Op-onal ͷ flatMap • Array ͷ flatMap • Observable ͷ flatMap
3. flatMap ͷҹ৅ɾɾɾ • Α͘Θ͔Βͳ͍΋ͷͱ͍͏ҹ৅͕͋Δʁ • ίʔυ͕ಡΈͮΒ͘ͳΔʁ • ͳΜ͔ map ͯ͠ fla'en ͢Δ΍ͭʁ • ؔ਺ܕʁ Ϟφυʁ
4. flatMap • ݸਓతʹ͸ɺؾָʹ࢖͑͹͍͍ͱࢥ͏ • ࢖ͬͯ׳Εͯ͠·͑͹ɺ೉͍͠΋ͷͰ͸ͳ͍
5. Op#onal ͷ flatMap
6. Op#onal ͷ flatMap • ม׵લ : Optional<T> • ม׵ॲཧ : T -> Optional<U> • flatMap : Optional<T> -> Optional<U> • ม׵લ͕ non-nil ͳΒม׵ॲཧΛద༻͢Δ • ม׵લ͕ nil ͳΒม׵ॲཧΛద༻͠ͳ͍
7. ྫ • ม׵લ : Optional<String> • ม׵ॲཧ : String -> Optional<Int> : { Int($0) } • string.flatMap { Int($0) } • "123" -> Int("123") -> 123 • "abc" -> Int("abc") -> nil • nil -> nil
8. nil ͷೖྗΛҙࣝ͠ͳ͍͍ͯ͘ // string ͸ Optional ͚ͩͲɾɾɾ let string: String? = "123" let integer: Int? = string.flatMap { Int($0) // $0 ͸ unwrap ͞Ε͍ͯΔ }
9. if let Ͱॻ͘ͱ৑௕ʹͳΔ let string: String? = "123" let integer: Int? if let string = string { integer = Int(string) } else { integer = nil }
10. Op#onal chaining ෩ʹ࢖͏ // Optional chaining string?.isEmpty // ಉ༷ʹ͜Μͳ΋ͷ͕ཉ͘͠ͳΔʁ string?.toInt // ୅ΘΓʹ͜͏͢Δ string.flatMap { Int($0) }
11. Array ͷ flatMap
12. Array ͷ flatMap • 2 छྨͷ flatMap ͕ଘࡏ͢Δ
13. Array ͷ flatMap (1) • ม׵લ : Array<T> • ม׵ॲཧ : T -> Array<U> • flatMap : Array<T> -> Array<U>
14. ྫ • ม׵લ : Array<Int> • ม׵ॲཧ : Int -> Array<Int> : { [$0, $0 * 10] } • [1, 2, 3].flatMap { [$0, $0 * 10] } • 1 -> [1, 10], 2 -> [2, 20], 3 -> [3, 30] • [1, 10, 2, 20, 3, 30]
15. Op#onal ͱ Array ͷ flatMap ൺֱ • ม׵લ : Optional<T> • ม׵ॲཧ : T -> Optional<U> • flatMap : Optional<T> -> Optional<U> • ม׵લ : Array<T> • ม׵ॲཧ : T -> Array<U> • flatMap : Array<T> -> Array<U>
16. flatMap ͷجຊܗ • ܕ T ΍ U ͕ೖͬͨԿΒ͔ͷശʢBoxʣ͕͋Δͱ͖ʹ • ม׵લ : Box<T> • ม׵ॲཧ : T -> Box<U> • flatMap : Box<T> -> Box<U>
17. Array ͷ flatMap (2) • ม׵લ : Array<T> • ม׵ॲཧ : T -> Optional<U> • flatMap : Array<T> -> Array<U> • ม׵ॲཧͷ݁Ռ͕ non-nil ͷ΋ͷ͕ Array ͷཁૉʹͳΔ • ม׵ॲཧͷ݁Ռ͕ nil ͷ΋ͷ͸ࣺͯΒΕΔ
18. ྫ • ม׵લ : Array<String> • ม׵ॲཧ : String -> Optional<Int> : { Int($0) } • ["123", "abc"].flatMap { Int($0) } • "123" -> 123, "abc" -> nil • [123]
19. Array ͷ 2 ͭͷ flatMap ͷؔ܎ • flatMap (2) ͸ flatMap (1) Ͱ࣮ݱͰ͖Δ • non-nil Λฦ͢୅ΘΓʹ1ཁૉͷ Array Λฦ͢ • nil Λฦ͢୅ΘΓʹۭͷ Array Λฦ͢ • flatMap (2) ͷํ͕ίʔυ͕γϯϓϧʹͳΔ • flatMap (1) ͸࣮͸͋Μ·Γ࢖Θͳ͍
20. ׆༻ྫ • ["A", "B", nil, "C"] : [String?] • ͔͜͜Β nil ΛऔΓআ͍ͨ [String] ͕ཉ͍͠ // flatMap ͳ͠ͳΒɺ͜Μͳײ͡Ͱॻ͘ʁ ["A", "B", nil, "C"] .filter({ $0 != nil }) as! [String]
21. ׆༻ྫ // ୯ʹ͜͏ॻ͚͹ྑ͍ ["A", "B", nil, "C"].flatMap { $0 } • ม׵લ : Array<Optional<String>> • ม׵ॲཧ : Optional<String> -> Optional<String> • flatMap : Array<Optional<String>> -> Array<String>
22. flatMap Λ׆༻͢Δ৔໘ • Op$onal ͱͷ૬ੑ͕ྑ͍ • Op$onal Λѻ͏ॲཧ͕͋Δͱ͖ʹ࢖͑ͳ͍͔ߟ͑Δͱྑ͍
23. ࢀߟɿଞʹ flatMap ͕࢖͑Δ΋ͷ • Result ܕʢan+typical/Resultʣ • Op+onal ͱ΄΅ಉ͡ʢnil ͷ୅ΘΓʹ۩ମతͳ Error Λฦ͢ʣ • Observable ܕʢRxSwi:ʣ • ඇಉظετϦʔϜɺ్தͰΤϥʔʹͳͬͨ৔߹ͷରԠ͕༰қ
24. Observable ͷ flatMap
25. Observable ͷ flatMap • ม׵લ : Observable<T> • ม׵ॲཧ : T -> Observable<U> • flatMap : Observable<T> -> Observable<U> • ม׵લ͕ .next ͳΒม׵ॲཧΛద༻͢Δ • ม׵લ͕ .error / .complete ͳΒม׵ॲཧΛద༻͠ͳ͍
26. ྫ Observable.of("123", "abc") .flatMap { string -> Observable<Int> in if let integer = Int(string) { return Observable.just(integer) } else { return Observable.empty() } } // -> [.next(123), .completed] • ิ଍ɿ্هͷ if let ͸ Op*onal ͷ flatMap Ͱॻ͘ͱεοΩϦ͢ Δ
27. Observable ͷ flatMap ͷ஫ҙ఺ • ม׵ॲཧ : T -> Observable<U> • flatMap : Observable<T> -> Observable<U> • ม׵ॲཧʹΑͬͯੜ੒͞Εͨ Observable<U> ΛɺflatMap ͸ Ͳ͏݁߹ͯ͠࠷ऴతͳ Observable<U> ʹ͢Δ͔ʁ • Op*onal ΍ Array ͷ৔߹ʹ͸ฆΕ͸ͳ͔ͬͨ • Observable ͸݁߹ͷ࢓ํ͕ෳ਺͋Δ
28. flatMap Ͱͷ݁߹ॲཧ • flatMap ͸ Observable Λ merge Ͱ݁߹͢Δʢconcat Ͱ͸ͳ ͍ʣ
29. ଞͷ݁߹Λߦ͏ flatMap • flatMapLatest ͸ switchLatest Ͱ݁߹͢Δ
30. flatMap Λ্खʹ׆༻͠Α͏