Swift Optional Extension Tips

Transcript

1. Optional Extension Tips Kyobashi.swift #2 @horimislime
2. About • ! @horimislime • " ҿ৯ళ޲͚iPadΞϓϦʮτϨλʯ • ❤ ιϑτ΢ΣΞઃܭͱ͔ӡ༻ͱ͔
3. Optionalͷ஍ຯͳπϥΈ
4. Objective-C if (users.count == 0) { // nil͔ۭͩͬͨΒԿ͔͢Δ } if (name.length == 0) { // ໊લ͕nil͔ۭͩͬͨΒԿ͔͢Δ }
5. Swift // Compile error ! if users?.isEmpty { // ... } if name?.isEmpty { // ... }
6. OptionalΛѻ͏ࡍͷ͓໿ଋ guard let users = users where !users.isEmpty else { // nil͔ۭͩͬͨΒԿ͔͢Δ }
7. Nil Coalescing • ୹͘ॻ͚Δ͕ɺͺͬͱݟͷՄಡੑʹ͚ܽΔ if array?.isEmpty ?? false { // ... } if !(str ?? "").isEmpty { // ... }
8. θϩ൑ఆ • nilͷൺֱ͸ৗʹfalse • Objective-C→Swiftʹࣸܦ͢Δͱ௧͍໨ʹ // Objective-C if (str.count == 0) { ... } /// Swift if str?.characters.count == 0 { ... }
9. ໰୊ • ܕ͕ݫີʹͳͬͨ΋ͷͷɺʮۭʯͷѻ͍͕໘౗ • nilͱۭͷঢ়ଶΛಉ͡Α͏ʹѻ͏ʹ͸ʁ
10. Optional Extension • isNilOrEmptyతͳ΋ͷ • ௚઀Optional<String>ʹextension͸ੜ΍ͤͳ͍ // Error: 'Wrapped' constrained to non-protocol type 'String' extension Optional where Wrapped: String { var isNilOrEmpty: Bool { return self?.isEmpty ?? true } }
11. Optional Extension • ಠࣗprotocolΛ༻ҙ͠ɺStringʹ४ڌͤ͞Δ protocol StringType { var isEmpty: Bool { get } } extension String: StringType {} extension Optional where Wrapped: StringType { var isNilOrEmpty: Bool { return self?.isEmpty ?? true } }
12. /// Before if name == nil || name.isEmpty else { // nil͔ۭͩͬͨΒԿ͔͢Δ } /// After if name.isNilOrEmpty { ... }
13. ·ͱΊ • nilͱۭ͸ҰॹͰߟ͑Δ৔߹͕ଟ͍ • ஍ຯͳͱ͜ΖͰՄಡੑΛམͱ͞ͳ͍Ұ޻෉ • Objective-C͔ΒSwiftҠߦظʹ͋Δͱศར͔΋