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

Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved.
USFBTUSBJO5BOBLB3ZPHB
ͦͷ4XJGUίʔυɺ
 
͜͏ॻ͖׵͑ͯΈͳ͍͔
1PMJTIJOHZPVS4XJGUDPEFXJUINF
1
DeNA
×
STORES
×
ϥΫϚ iOS Meetup!! #dena_stores_rakuma

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"CPVUNF
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2
4XJGU J04 XBUDI04 $PSF/'$
044
 
ɹɹJU`TNZNPUIFSUPOHVF
 
ɹɹ࠷ۙ#MVFTLZΛ͸͡Ί·ͨ͠
ɹɹɹɹɹɹɹɹɹɹ!USFBTUSBJOɹɹIUUQTUSFUKQ
 
 
%F/"$P -UE
 
ɹɹJ04"QQ%FWFMPQFSʢ"QSJM$VSSFOUʣ

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BoolΛ൓స͢Δʹ͸toggle()Λ࢖͏
flag = !flagΑΓΘ͔Γ΍͍͢
w !Ͱ൓సͰ͖Δ͚Ͳʜʜ
3
var flag = true

flag = !flag

print(flag) // false

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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

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w toggle()ͰಡΈ΍͘͢ɺهड़ϛεͷ৺഑΋ݮΔ
5
flag.toggle()

hoge.fuga1.piyo2.flag.toggle()

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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

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ίϨΫγϣϯͷendIndexΛ࢖͏
countͬΆ͍͚ΕͲ
w ʮ࠷ޙͷΠϯσοΫεʯΛࣔ͢
w count͸0 O
ɺendIndex͸0

7
let list = ["DeNA", "STORES", "Rakuten Rakuma”]

print(list.count) // 3

print(list.endIndex) // 3

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ίϨΫγϣϯ͕ۭ͔Ͳ͏͔͸isEmptyͰಘΔ
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

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ίϨΫγϣϯͷΠϯσοΫε͸indexed()ͰಘΔ
enumerated()΍zip(_:_:)Ͱ͸ͳ͘
w enumerated()͸ཁૉͱҰॹʹʮ0͔Β࢝·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

*/

}

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w ʮ0͔Β࢝·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

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w ඪ४తͳ୅ସҊzip(_:_:)͸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


*/

}

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w 4XJGU"MHPSJUINTͷindexed()͸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


*/

}

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ೋॏͷϧʔϓ͸product(_:_:)Λ࢖͏
for-inΛճॻ͘ඞཁ͕ͳ͘ͳΔ
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

...

*/

}

}

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ೋॏͷϧʔϓ͸product(_:_:)Λ࢖͏
for-inΛճॻ͘ඞཁ͕ͳ͘ͳΔ
w 4XJGU"MHPSJUINTͷproduct(_:_:)ͰωετΛݮΒͤΔ
w Ұํ͕ۭͷ৔߹ɺແବͳϧʔϓॲཧ͕ൃੜ͠ͳ͍
14
import Algorithms

for (year, month) in product(years, months) {

print(year, month)

}

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for-inͱforEach(_:)ͷ࢖͍෼͚Λߟ͑ͯΈΔ
forEach(_:)ࣗମ͸for-inͰ࣮૷͞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

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for-inͱforEach(_:)ͷ࢖͍෼͚Λߟ͑ͯΈΔ
forEach(_:)ࣗମ͸for-inͰ࣮૷͞Ε͍ͯΔ͚Ͳ
16
for-inϧʔϓ forEach(_:)
ϧʔϓΛ్தͰ΍ΊΔ breakΛ࢖͏ Ͱ͖ͳ͍
ॲཧͷ్தͰ࣍ͷཁૉʹҠΔ continueΛ࢖͏ returnΛ࢖͏
SFUVSOจΛ࢖͏ͱ ϧʔϓ͕͋Δείʔϓ͔Βग़Δ ࣍ͷཁૉͷॲཧʹҠΔ
ཁૉ໊ͷলུ Ͱ͖ͳ͍ Ͱ͖Δʢ$0ʣ
ؔ਺ͳͲΛ௚઀౉͢ Ͱ͖ͳ͍ Ͱ͖ΔʢforEach(someFunc())ʣ
ඇಉظʢBTZODBXBJUʣॲཧ Ͱ͖Δ Ͱ͖ͳ͍

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໊લۭؒʢ/BNFTQBDFTʣʹ͸enumΛ࢖͏
class΍structͰ͸ͳ͘
w struct΍classΛ࢖͏ͱɺ
 
internalͰ࢖͑ΔΠχγϟϥΠβ͕σϑΥϧτͰ༻ҙ͞Εͯ͠·͏
17
enum BreakfastMenu {

static let rice = "͝൧"

static let bread = "ύϯ"

// ...

}

print(BreakfastMenu.rice) // ͝൧

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ϥϯμϜͳ஋ɾཁૉ͕΄͍͠
arc4random()΍arc4random_uniform(_:)͸࢖Θͳ͍
w 4XJGU͔Β࢖͑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()

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Optional.map(_:)Λ࢖͏
nilͷͱ͖͸nilͷ··ɺnilͰͳ͍ͱ͖͚ͩॲཧΛߦ͏
w nilͷͱ͖͸ʜͷ෼ذΛࣗ෼Ͱॻ͔ͳͯ͘ࡁΉ
19
struct Talk {

let title: String

}

let selectedTalkTitle: String? = nil

let selectedTalk: Talk? = selectedTalkTitle.map { Talk(title: $0) }

print(selectedTalk) // nil

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ʮOptionalͳvarʯΛʮඇ0QUJPOBMͳletʯʹ
ʮHFU͢Δͱ͖·Ͱʹ͸ඞͣTFU͞Ε͍ͯΔʯϓϩύςΟͰ
20
enum Area {

case osaka, hiroshima

}

let area: Area = // ...

var okonomiyaki: String?

switch area {

case .osaka:

okonomiyaki = "ؔ੢෩"

case .hiroshima:

okonomiyaki = "޿ౡ෩"

}

print(okonomiyaki)

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ʮOptionalͳvarʯΛʮඇ0QUJPOBMͳletʯʹ
ʮHFU͢Δͱ͖·Ͱʹ͸ඞͣTFU͞Ε͍ͯΔʯϓϩύςΟͰ
21
enum Area {

case osaka, hiroshima

}

let area: Area = // ...

let okonomiyaki: String

switch area {

case .osaka:

okonomiyaki = "ؔ੢෩"

case .hiroshima:

okonomiyaki = "޿ౡ෩"

}

print(okonomiyaki)

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͋ͱ͔ΒTFU͞ΕΔϓϩύςΟΛOptionalʹ͠ͳ͍
ඞͣTFU͞ΕΔͳΒpreconditionFailure(_: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!)

}

}

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͋ͱ͔ΒTFU͞ΕΔϓϩύςΟΛOptionalʹ͠ͳ͍
ඞͣTFU͞ΕΔͳΒpreconditionFailure(_: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)

}

}

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֦ு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)

}

}

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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)

}

}

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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)

}

}

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w 4XJGU6*ͷྫ
27
import SwiftUI

struct ContentView: View {


}

extension ContentView {

var body: some View { // 😫 ҉໧తʹ @MainActor Ͱ͸ͳ͘ͳΓɺ

// ϓϩτίϧ View ଆͷఆٛͱ͸ҟͳͬͯ͠·͏

Text(greeting)

}

}

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w 4XJGU6*ͷྫ
28
import SwiftUI

struct ContentView {


}

extension ContentView: View {

var body: some View { // ✅ ϓϩτίϧ View ଆͷఆٛΑΓ

// ҉໧తʹ @MainActor ʹͳΔ

Text(greeting)

}

}

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ͦͷ΄͔఻͔͑ͨͬͨ͜ͱ
͕࣌ؒ଍Γͳ͔ͬͨʜʜ
w switchจͰͪΌΜͱ໢ཏͯ͠ɺ
 
ݟམͱ͠Λແͨ͘͠Γޙͷมߋʹڧͨ͘͠Γ͢Δ
w Resultͱεϩʔؔ਺ʢ5ISPXJOH'VODUJPOTʣͷ૬ޓม׵
w %FMFHBUFɾΫϩʔδϟΛBTZODͳؔ਺ʹ͢Δ
w NotificationCenterΛ4XJGU$PODVSSFODZ͔Β࢖͏
w $PNCJOFɾ3Y4XJGUΛ4XJGU$PODVSSFODZ͔Β࢖͏
29

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͞ΒʹεςοϓΞοϓ
6*,JUʢJ04ͳͲʣͰʮͬͪ͜ͷํ͕͍͍Αʯ
30

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ɹɹɹɹɹεϥΠυɾൃද಺༰͸IUUQTUSFUKQͰެ։͍ͯ͠·͢ɹ⏩
ͦͷ4XJGUίʔυɺ
 
͜͏ॻ͖׵͑ͯΈͳ͍͔
1PMJTIJOHZPVS4XJGUDPEFXJUINF
31
DeNA
×
STORES
×
ϥΫϚ iOS Meetup!! #dena_stores_rakuma

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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!

treastrain / Tanaka Ryoga

More Decks by treastrain / Tanaka Ryoga

Other Decks in Programming

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Transcript

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!

treastrain / Tanaka Ryoga

More Decks by treastrain / Tanaka Ryoga

Other Decks in Programming

Featured

Transcript

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!