今日から使える！ Optionalをいい感じに扱うtips

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1. ࠓ೔͔Β࢖͑Δʂ OptionalΛ͍͍ײ͡ʹѻ͏tips 2019/3/19 ͋Δ͋ΔLTʙεϚϗΞϓϦ։ൃΤϯδχΞʙ Vol.3 PKPK-Carnage(Tomosuke Okada)
2. About me • iOSྺ2೥ͪΐͬͱ • Qiita → @PKPK-Carnage • Github → PKPK-Carnage • Twitter → @PKPK-Carnage
3. ࠷ۙࢥͬͨ͜ͱɾɾɾ 3
4. 4 OptionalΛ੍͢Δऀ͸SwiftΛ੍͢!!
5. tips1: switch 5
6. switch 6 enum TestType: Int { case hoge = 0 case fuga = 1 case piyo = 2 }
7. switch 7 func generateText(from index: Int) -> String { guard let unwrappedType = TestType(rawValue: index) else { return "" } switch unwrappedType { case .hoge: return "Hoge" case .fuga: return "Fuga" case .piyo: return "Piyo" } }
8. case?ͱ.noneΛ࢖͏ͱɾɾɾ 8
9. switch 9 func generateText(from index: Int) -> String { guard let unwrappedType = TestType(rawValue: index) else { return "" } switch unwrappedType { case .hoge: return "Hoge" case .fuga: return "Fuga" case .piyo: return "Piyo" } }
10. switch 10 func generateText(from index: Int) -> String { switch TestType(rawValue: index) { case .hoge?: return "Hoge" case .fuga?: return "Fuga" case .piyo?: return "Piyo" case .none: return "" } }
11. switchͷ൑ఆର৅͕nilͩͬͨ৔߹ͷॲཧΛ .none಺ʹهड़Ͱ͖Δʂ 11
12. tips2: Nil Coalescing Operator + Closure 12
13. Nil Coalescing Operator 13 let text = "" let intValue = Int(text) == nil ? 0 : Int(text)!
14. Nil Coalescing Operator 14 let text = "" let intValue = Int(text) ?? 0
15. ཁ͢Δʹࡾ߲ԋࢉࢠͷলུ 15
16. ??ͷޙʹ͸Closure΋ࢦఆͰ͖Δ 16
17. Nil Coalescing Operator 17 let text = "" let intValue = Int(text) ?? 0
18. Nil Coalescing Operator + Closure 18 let text = "" let intValue = Int(text) ?? { return 0 }()
19. ͜ΕͰ͖ͯԿʹͳΔͷʁ 19
20. ׆༻๏ 20 let text = "" let intValue = Int(text) ?? { return 0 }()
21. ׆༻๏ 21 let text = "" let intValue = Int(text) ?? { assertionFailure("਺ࣈͷςΩετ͕ೖͬͯ·ͤΜʂ") return 0 }()
22. σόοάϏϧυͷ͚࣌ͩnilͩͬͨ࣌ʹ Ϋϥογϡͤ͞ΒΕΔ 22
23. ·ͱΊ • optionalͷΦϒδΣΫτΛswitchʹ͢Δͱ͖͸ɺcase? ͱ.noneΛ࢖͏ͱΞϯϥοϓ͢Δඞཁ͕ͳ͍ • ??ͷޙʹ͸ClosureΛೖΕΔ͜ͱ͕Ͱ͖ΔͷͰɺ͔ͳΓࣗ༝ ౓͕ߴ͍ɻ 23
24. ͓ΘΓ 24