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΋

14. None