その Swift コード、 こう書き換えてみないか / Polishing your Swift code with me!

その Swift コード、
こう書き換えてみないか / Polishing your Swift code with me!

DeNA×STORES×ラクマ iOS Meetup!!
2023/05/22 19:00〜
https://connpass.com/event/283989/

登壇ノートはこちら: https://zenn.dev/treastrain/articles/65f6cae11e0dc7

Transcript

1. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. USFBTUSBJO
   
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   NF 1 DeNA × STORES × ϥΫϚ iOS Meetup!! #dena_stores_rakuma
2. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. "CPVU
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3. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Bool
   Λ൓స͢Δʹ͸
   toggle()
   Λ࢖͏ flag = !flag
   ΑΓΘ͔Γ΍͍͢ w !
   Ͱ൓సͰ͖Δ͚Ͳʜʜ 3 var flag = true flag = !flag print(flag) // false
4. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Bool
   Λ൓స͢Δʹ͸
   toggle()
   Λ࢖͏ flag = !flag
   ΑΓΘ͔Γ΍͍͢ 4 struct Hoge { var fuga1 = Fuga(); var fuga2 = Fuga() struct Fuga { var piyo1 = Piyo(); var piyo2 = Piyo() struct Piyo { var flag = true } } } var hoge = Hoge() hoge.fuga1.piyo2.flag = !hoge.fuga2.piyo1.flag // fuga1ɾ2ɺpiyo2ɾ1 ͕ٯʂ
5. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Bool
   Λ൓స͢Δʹ͸
   toggle()
   Λ࢖͏ flag = !flag
   ΑΓΘ͔Γ΍͍͢ w toggle()
   ͰಡΈ΍͘͢ɺهड़ϛεͷ৺഑΋ݮΔ 5 flag.toggle() hoge.fuga1.piyo2.flag.toggle()
6. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. isMultiple(of:)
   Λ࢖͏ x % 2 == 0
   ͸࢖Θͳ͍ w ӳޠͷจষͷΑ͏ʹಡΊͯɺՄಡੑ͕޲্ 6 let x = 4 print(x % 2 == 0) // true - `%` ԋࢉࢠΛ༻͍Δྫ print(x & 1 == 0) // true - `&` ԋࢉࢠΛ༻͍Δྫ print(x.isMultiple(of: 2)) // true - ӳޠͷจষͷΑ͏ʹಡΊΔ print(x.isMultiple(of: 3)) // false
7. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯͷ
   endIndex
   Λ࢖͏ count
   ͬΆ͍͚ΕͲ w ʮ࠷ޙͷΠϯσοΫε ʯΛࣔ͢
   w count
   ͸
   0 O ɺendIndex
   ͸
   0  7 let list = ["DeNA", "STORES", "Rakuten Rakuma”] print(list.count) // 3 print(list.endIndex) // 3
8. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯ͕ۭ͔Ͳ͏͔͸
   isEmpty
   ͰಘΔ count == 0
   ͸࢖Θͳ͍ w ಡΈ΍͍͢
   w count
   ͸
   0 O ɺisEmpty
   ͸
   0  8 let list1 = ["DeNA", "STORES", "Rakuten Rakuma"] print(list1.count == 0) // false print(list1.isEmpty) // false var list2 = list1 list2.removeAll() print(list2.count == 0) // true print(list2.isEmpty) // true
9. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯͷΠϯσοΫε͸
   indexed()
   ͰಘΔ enumerated()
   ΍
   zip(_:_:)
   Ͱ͸ͳ͘ w enumerated()
   ͸ཁૉͱҰॹʹʮ0
   ͔Β࢝·Δ࿈൪ʯΛฦ͢ 9 let prefectures = ["Hokkaido", "Aomori", "Iwate", "Miyagi", "Akita", "Yamagata", “Fukushima"] for (offset, prefecture) in prefectures.enumerated() { print(offset, prefecture, prefectures[offset]) /* 0 Hokkaido Hokkaido 1 Aomori Aomori 2 Iwate Iwate 3 Miyagi Miyagi 4 Akita Akita 5 Yamagata Yamagata 6 Fukushima Fukushima */ }
10. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯͷΠϯσοΫε͸
    indexed()
    ͰಘΔ enumerated()
    ΍
    zip(_:_:)
    Ͱ͸ͳ͘ w ʮ0
    ͔Β࢝·Δ࿈൪ʯͱʮίϨΫγϣϯͷΠϯσοΫεʯ͸Ұக͠ͳ͍͔΋ 10 let tohoku = prefectures.dropFirst() for (offset, prefecture) in tohoku.enumerated() { print(offset, prefecture, prefectures[offset]) /* 0 Aomori Hokkaido 1 Iwate Aomori 2 Miyagi Iwate 3 Akita Miyagi 4 Yamagata Akita 5 Fukushima Yamagata */ } print(tohoku[0]) // 💥 Fatal error: Index out of bounds
11. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯͷΠϯσοΫε͸
    indexed()
    ͰಘΔ enumerated()
    ΍
    zip(_:_:)
    Ͱ͸ͳ͘ w ඪ४తͳ୅ସҊ
    zip(_:_:)
    ͸
    enumerated()
    ΑΓύϑΥʔϚϯε͕ѱ͍ 11 for (index, prefecture) in zip(tohoku.indices, tohoku) { print(index, prefecture, prefectures[index]) /* 1 Aomori Aomori 2 Iwate Iwate 3 Miyagi Miyagi 4 Akita Akita 5 Yamagata Yamagata 6 Fukushima Fukushima */ }
12. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ίϨΫγϣϯͷΠϯσοΫε͸
    indexed()
    ͰಘΔ enumerated()
    ΍
    zip(_:_:)
    Ͱ͸ͳ͘ w 4XJGU
    "MHPSJUINT
    ͷ
    indexed()
    ͸
    zip(_:_:)
    ΑΓ 
 ύϑΥʔϚϯε͕ྑ͍ 12 import Algorithms for (index, prefecture) in tohoku.indexed() { print(index, prefecture, prefectures[index]) /* 1 Aomori Aomori 2 Iwate Iwate 3 Miyagi Miyagi 4 Akita Akita 5 Yamagata Yamagata 6 Fukushima Fukushima */ }
13. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ೋॏͷϧʔϓ͸
    product(_:_:)
    Λ࢖͏ for-in
    Λճॻ͘ඞཁ͕ͳ͘ͳΔ 13 let years = [2021, 2022, 2023] let months = ["January", "February", "March", /* ... */] for year in years { for month in months { print(year, month) /* 2021 January 2021 February 2021 March ... 2022 January 2022 February 2022 March ... */ } }
14. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ೋॏͷϧʔϓ͸
    product(_:_:)
    Λ࢖͏ for-in
    Λճॻ͘ඞཁ͕ͳ͘ͳΔ w 4XJGU
    "MHPSJUINT
    ͷ
    product(_:_:)
    ͰωετΛݮΒͤΔ
    w Ұํ͕ۭͷ৔߹ɺແବͳϧʔϓॲཧ͕ൃੜ͠ͳ͍ 14 import Algorithms for (year, month) in product(years, months) { print(year, month) }
15. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. for-in
    ͱ
    forEach(_:)
    ͷ࢖͍෼͚Λߟ͑ͯΈΔ forEach(_:)
    ࣗମ͸
    for-in
    Ͱ࣮૷͞Ε͍ͯΔ͚Ͳ 15 func printWithLowercased(_ value: String) { print(value.lowercased()) } let list = ["DeNA", "STORES", "Rakuten Rakuma"] for name in list { printWithLowercased(name) } // ಉ͡ग़ྗ list.forEach { name in printWithLowercased(name) } // ಉ͡ग़ྗ
16. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. for-in
    ͱ
    forEach(_:)
    ͷ࢖͍෼͚Λߟ͑ͯΈΔ forEach(_:)
    ࣗମ͸
    for-in
    Ͱ࣮૷͞Ε͍ͯΔ͚Ͳ 16 for-in
    ϧʔϓ forEach(_:) ϧʔϓΛ్தͰ΍ΊΔ break
    Λ࢖͏ Ͱ͖ͳ͍ ॲཧͷ్தͰ࣍ͷཁૉʹҠΔ continue
    Λ࢖͏ return
    Λ࢖͏ SFUVSO
    จΛ࢖͏ͱ ϧʔϓ͕͋Δείʔϓ͔Βग़Δ ࣍ͷཁૉͷॲཧʹҠΔ ཁૉ໊ͷলུ Ͱ͖ͳ͍ Ͱ͖Δʢ$0ʣ ؔ਺ͳͲΛ௚઀౉͢ Ͱ͖ͳ͍ Ͱ͖ΔʢforEach(someFunc())ʣ ඇಉظʢBTZODBXBJUʣॲཧ Ͱ͖Δ Ͱ͖ͳ͍
17. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ໊લۭؒʢ/BNFTQBDFTʣʹ͸
    enum
    Λ࢖͏ class
    ΍
    struct
    Ͱ͸ͳ͘ w struct
    ΍
    class
    Λ࢖͏ͱɺ 
 internal
    Ͱ࢖͑ΔΠχγϟϥΠβ͕σϑΥϧτͰ༻ҙ͞Εͯ͠·͏ 17 enum BreakfastMenu { static let rice = "͝൧" static let bread = "ύϯ" // ... } print(BreakfastMenu.rice) // ͝൧
18. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ϥϯμϜͳ஋ɾཁૉ͕΄͍͠ arc4random()
    ΍
    arc4random_uniform(_:)
    ͸࢖Θͳ͍ w 4XJGU
    
    ͔Β࢖͑ΔΑ͏ʹͳͬͨ 
 random()ɾrandom(in:)ɾrandomElement()
    Λ࢖͏ 18 let flag = Bool.random() let num = Int.random(in: 0..<10) let area = [1: "Shibuya", 2: "Shinjuku"].randomElement() let player = ["uhooi", "treastrain"].randomElement()
19. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Optional.map(_:)
    Λ࢖͏ nil
    ͷͱ͖͸
    nil
    ͷ··ɺnil
    Ͱͳ͍ͱ͖͚ͩॲཧΛߦ͏ w nil
    ͷͱ͖͸ʜ
    ͷ෼ذΛࣗ෼Ͱॻ͔ͳͯ͘ࡁΉ 19 struct Talk { let title: String } let selectedTalkTitle: String? = nil let selectedTalk: Talk? = selectedTalkTitle.map { Talk(title: $0) } print(selectedTalk) // nil
20. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ʮOptional
    ͳ
    varʯΛʮඇ0QUJPOBM
    ͳ
    letʯʹ ʮHFU
    ͢Δͱ͖·Ͱʹ͸ඞͣ
    TFU
    ͞Ε͍ͯΔʯϓϩύςΟͰ 20 enum Area { case osaka, hiroshima } let area: Area = // ... var okonomiyaki: String? switch area { case .osaka: okonomiyaki = "ؔ੢෩" case .hiroshima: okonomiyaki = "޿ౡ෩" } print(okonomiyaki)
21. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ʮOptional
    ͳ
    varʯΛʮඇ0QUJPOBM
    ͳ
    letʯʹ ʮHFU
    ͢Δͱ͖·Ͱʹ͸ඞͣ
    TFU
    ͞Ε͍ͯΔʯϓϩύςΟͰ 21 enum Area { case osaka, hiroshima } let area: Area = // ... let okonomiyaki: String switch area { case .osaka: okonomiyaki = "ؔ੢෩" case .hiroshima: okonomiyaki = "޿ౡ෩" } print(okonomiyaki)
22. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ͋ͱ͔Β
    TFU
    ͞ΕΔϓϩύςΟΛ
    Optional
    ʹ͠ͳ͍ ඞͣ
    TFU
    ͞ΕΔͳΒ
    preconditionFailure(_:file:line:)
    ΛԾஔ͖͢Δ 22 import UIKit final class ViewController: UIViewController { // ͜ͷ collectionView ͸ viewDidLoad() ͷޙʹ࡞Δ͜ͱʹ͍ͯ͠ΔʢͱԾఆʣ private var collectionView: UICollectionView? override func viewDidLoad() { super.viewDidLoad() // collectionView Λ࡞Δ collectionView = UICollectionView(frame: .null) // ... // collectionView Λ࢖͏ view.addSubview(collectionView!) } }
23. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ͋ͱ͔Β
    TFU
    ͞ΕΔϓϩύςΟΛ
    Optional
    ʹ͠ͳ͍ ඞͣ
    TFU
    ͞ΕΔͳΒ
    preconditionFailure(_:file:line:)
    ΛԾஔ͖͢Δ 23 import UIKit final class ViewController: UIViewController { // ͜ͷ collectionView ͸ viewDidLoad() ͷޙʹ࡞Δ͜ͱʹ͍ͯ͠ΔʢͱԾఆʣ private lazy var collectionView: UICollectionView = { preconditionFailure("collectionView has not been set") }() override func viewDidLoad() { super.viewDidLoad() // collectionView Λ࡞Δ collectionView = UICollectionView(frame: .null) // ... // collectionView Λ࢖͏ view.addSubview(collectionView) } }
24. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ֦ுʢ&YUFOTJPOTʣ͸ϓϩτίϧʢ1SPUPDPMTʣ͝ͱʹ࡞Δ ͦͷϓϩτίϧ΁ͷ४ڌͷͨΊͷ࣮૷͸ͦͷதͰͷΈߦ͏ 24 import Foundation struct Book { let name: String let uuid: UUID } extension Book: Identifiable, Hashable { var id: UUID { uuid } } extension Book { func hash(into hasher: inout Hasher) { hasher.combine(id) } }
25. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ֦ுʢ&YUFOTJPOTʣ͸ϓϩτίϧʢ1SPUPDPMTʣ͝ͱʹ࡞Δ ͦͷϓϩτίϧ΁ͷ४ڌͷͨΊͷ࣮૷͸ͦͷதͰͷΈߦ͏ 25 import Foundation struct Book { let name: String let uuid: UUID } extension Book: Identifiable { var id: UUID { uuid } } extension Book: Hashable { func hash(into hasher: inout Hasher) { hasher.combine(id) } }
26. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ֦ுʢ&YUFOTJPOTʣ͸ϓϩτίϧʢ1SPUPDPMTʣ͝ͱʹ࡞Δ ͦͷϓϩτίϧ΁ͷ४ڌͷͨΊͷ࣮૷͸ͦͷதͰͷΈߦ͏ w 4XJGU6*
    ͷྫ 26 import SwiftUI struct ContentView: View { let greeting = "Hello, happy world!" var body: some View { // ϓϩτίϧ View ଆͷఆٛͰ @MainActor ʹͳ͍ͬͯΔ Text(greeting) } }
27. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ֦ுʢ&YUFOTJPOTʣ͸ϓϩτίϧʢ1SPUPDPMTʣ͝ͱʹ࡞Δ ͦͷϓϩτίϧ΁ͷ४ڌͷͨΊͷ࣮૷͸ͦͷதͰͷΈߦ͏ w 4XJGU6*
    ͷྫ 27 import SwiftUI struct ContentView: View { let greeting = "Hello, happy world!" } extension ContentView { var body: some View { // 😫 ҉໧తʹ @MainActor Ͱ͸ͳ͘ͳΓɺ // ϓϩτίϧ View ଆͷఆٛͱ͸ҟͳͬͯ͠·͏ Text(greeting) } }
28. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ֦ுʢ&YUFOTJPOTʣ͸ϓϩτίϧʢ1SPUPDPMTʣ͝ͱʹ࡞Δ ͦͷϓϩτίϧ΁ͷ४ڌͷͨΊͷ࣮૷͸ͦͷதͰͷΈߦ͏ w 4XJGU6*
    ͷྫ 28 import SwiftUI struct ContentView { let greeting = "Hello, happy world!" } extension ContentView: View { var body: some View { // ✅ ϓϩτίϧ View ଆͷఆٛΑΓ // ҉໧తʹ @MainActor ʹͳΔ Text(greeting) } }
29. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ͦͷ΄͔
    ఻͔͑ͨͬͨ͜ͱ ͕࣌ؒ଍Γͳ͔ͬͨʜʜ w switch
    จͰͪΌΜͱ໢ཏͯ͠ɺ 
 ݟམͱ͠Λແͨ͘͠Γ
    ޙͷมߋʹڧͨ͘͠Γ͢Δ
    w Result
    ͱεϩʔؔ਺ʢ5ISPXJOH
    'VODUJPOTʣͷ૬ޓม׵
    w %FMFHBUFɾΫϩʔδϟΛ
    BTZOD
    ͳؔ਺ʹ͢Δ
    w NotificationCenter
    Λ
    4XJGU
    $PODVSSFODZ
    ͔Β࢖͏
    w $PNCJOFɾ3Y4XJGU
    Λ
    4XJGU
    $PODVSSFODZ
    ͔Β࢖͏ 29
30. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ͞ΒʹεςοϓΞοϓ 6*,JUʢJ04
    ͳͲʣͰʮͬͪ͜ͷํ͕͍͍Αʯ 30
31. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ɹɹɹɹɹ
    
    εϥΠυɾൃද಺༰͸
    IUUQTUSFUKQ
    Ͱެ։͍ͯ͠·͢ɹ⏩ ͦͷ
    4XJGU
    ίʔυɺ 
 ͜͏ॻ͖׵͑ͯΈͳ͍͔ 1PMJTIJOH
    ZPVS
    4XJGU
    DPEF
    XJUI
    NF 31 DeNA × STORES × ϥΫϚ iOS Meetup!! #dena_stores_rakuma