What’s new in Swift? (from WWDC 2020)

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1. What’s new in Swift? @Kaz_Homma (Kazutaka Homma)

2. @Kaz_Homma (本間 和尊) iOS Engineer at Mercari JP Joined on

   July, 2019 Github: @Kazutaka333 Twitter: @Kaz_Homma 2

3. 1. Multiple trailing closures 複数クロージャーでもカッコを省略して引数に書ける！ 2. Increased availability of implicit

   self in closures selfを書く回数が減る！ 3. Synthesized Comparable conformance for enum types enumにComparableプロトコルが使いやすくなった！ 4. Enum cases as protocol witnesses Enum caseでstatic var・static funcを満たすことができる！ 5. KeyPath expressions as function keyPathをクロージャーの代わりに渡せる！ Agenda 3

4. Multiple trailing closures SE-0279 // Trailing Closure なし UIView.animate(withDuration: 0.1,

   animations: { self.view.backgroundColor = .red }) // Trailing Closure あり // 引数の省略かつ、ネストを減らしたシンプルな見た目 UIView.animate(withDuration: 0.1) { self.view.backgroundColor = .red } 1/4 4

5. // Swift5.2 // Trailing Closureなし UIView.animate(withDuration: 0.3, animations: { self.view.alpha

   = 0 }, completion: { _ in self.view.removeFromSuperview() }) Multiple trailing closures SE-0279 2/4 // Trailing Closureあり // 引数名が省略されていて2つ目のclosureが // わかりにくい UIView.animate(withDuration: 0.3, animations: { self.view.alpha = 0 }) { _ in self.view.removeFromSuperview() } 5

6. // Swift5.2 // Multiple Trailing Closureなし // 引数名が省略されいて 2つ目のclosureがわかりにくい UIView.animate(withDuration:

   0.3, animations: { view.alpha = 0 }) { _ in view.removeFromSuperview() } Multiple trailing closures SE-0279 3/4 // Swift5.3 // Multiple trailing closureをつかうと… // 少ないネストかつ、2つ目のclosureの引数もあるので // わかりやすい UIView.animate(withDuration: 0.3) { view.alpha = 0 } completion: { _ in view.removeFromSuperview() } 6

7. // もっとmultiple trailing closures... func animate(animation: (() -> Void), preparation:

   (() -> Void), completion: ((Bool) -> Void)) { // hoge hoge... } animate { // animating... } preparation: { // preparing... } completion: { result in // completing task... } Multiple trailing closures SE-0279 4/4 7

8. // たくさんのself... UIView.animate(withDuration: 0.3) { self.recordingView?.alpha = 0.0 self.textView.alpha =

   1.0 } completion: { _ in self.activeTransitionCount -= 1 if !self.isRecording && self.activeTransitionCount == 0 { self.recordingView?.removeFromSuperview() self.recordingView = nil } } Increased availability of implicit self in closures SE-0269 1/4 8

9. Increased availability of implicit self in closures SE-0269 // Swift5.3ではselfをキャプチャすればclosure内で

   // 省略できる UIView.animate(withDuration: 0.3) { [self] in recordingView?.alpha = 0.0 textView.alpha = 1.0 } completion: { [self] _ in activeTransitionCount -= 1 if !isRecording && activeTransitionCount == 0 { recordingView?.removeFromSuperview() recordingView = nil } } // たくさんのself… UIView.animate(withDuration: 0.3) { self.recordingView?.alpha = 0.0 self.textView.alpha = 1.0 } completion: { _ in self.activeTransitionCount -= 1 if !self.isRecording && self.activeTransitionCount == 0 { self.recordingView?.removeFromSuperview() self.recordingView = nil } } 2/4 9

10. Increased availability of implicit self in closures SE-0269 // weak

    selfは今まで通りです UIView.animate(withDuration: 0.3) { [weak self] in guard let self = self else { return } self.recordingView?.alpha = 0.0 self.textView.alpha = 1.0 } UIView.animate(withDuration: 0.3) { [weak self] in self?.recordingView?.alpha = 0.0 self?.textView.alpha = 1.0 } 3/4 10

11. Increased availability of implicit self in closures SE-0269 4/4 11

12. Synthesized Comparable conformance for enum types SE-0266 12 1/3 //

    まずComparableとは? struct Date { let year: Int let month: Int let day: Int } extension Date: Comparable { static func < (lhs: Date, rhs: Date) -> Bool { if lhs.year != rhs.year { return lhs.year < rhs.year } else if lhs.month != rhs.month { return lhs.month < rhs.month } else { return lhs.day < rhs.day } } } print(Date(year: 10, month: 10, day: 10) > Date(year: 10, month: 10, day: 9)) // true

13. Synthesized comparable conformance for enum types SE-0266 // Swift 5.3未満

    enum Membership: Int, Comparable { case basic case silver case gold static func < (lhs: Self, rhs: Self) -> Bool { return lhs.rawValue < rhs.rawValue } } print(Membership.basic < Membership.silver) // true print(Membership.silver < Membership.gold) // true print(Membership.basic > Membership.gold) // false 13 2/3

14. Synthesized comparable conformance for enum types SE-0266 // Swift 5.3以前

    enum Membership: Int, Comparable { case basic case silver case gold static func < (lhs: Self, rhs: Self) -> Bool { return lhs.rawValue < rhs.rawValue } } print(Membership.basic < Membership.silver) // true print(Membership.silver < Membership.gold) // true print(Membership.basic > Membership.gold) // false 14 3/3 // Swift 5.3では簡略化できる enum Membership: Comparable { case basic case silver case gold } print(Membership.basic < Membership.silver) // true print(Membership.silver < Membership.gold) // true print(Membership.basic > Membership.gold) // false

15. Enum cases as protocol witnesses SE-0280 15 1/5

16. Enum cases as protocol witnesses SE-0280 16 2/2

17. KeyPath expressions as function SE-0249 17 1/4

18. KeyPath expressions as function SE-0249 18 2/4

19. KeyPath expressions as function SE-0249 19 3/4

20. KeyPath expressions as function SE-0249 20 4/4 Swift 5.2からは必要ない

21. 1. Multiple trailing closures 複数クロージャーでもカッコを省略して引数に書ける！ 2. Increased availability of implicit

    self in closures selfを書く回数が減る！ 3. Synthesized Comparable conformance for enum types enumにComparableプロトコルが使いやすくなった！ 4. Enum cases as protocol witnesses Enum caseでstatic var・static funcを満たすことができる！ 5. KeyPath expressions as function keyPathをクロージャーの代わりに渡せる！ おさらい 21

22. Thank you 22