20分でわかる！速習resultBuilder（iOSDC 2022）

Transcript

1. ɹɹ
   ©︎
   hey, Inc
   20分でわかる！速習resultBuilder
   
   
   ヘイ株式会社 テクノロジー部門 モバイルアプリケーション本部
   
   
   STORES レジ iOSエンジニア
   
   
   たまねぎ（Takuya Yokoyama）
   iOSDC2022
   

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2. ɹ
   ɹ
   自己紹介
   Profile {
   
   
   Name("ͨ·Ͷ͗")
   
   
   Twitter("@_chocoyama")
   
   
   Work {
   
   
   Company("hey inc")
   
   
   Product("STORES Regi")
   
   
   Role("Mobile Engineer")
   
   
   }
   
   
   
   
   Skill {
   
   
   SwiftUI()
   
   
   Flutter()
   
   
   Compose()
   
   
   }
   
   
   }
   

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3. ɹ
   ɹ
   

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4. ɹ
   ɹ
   発表のゴール
   ●resultBuilderとは何かがわかる
   
   
   ●実装方法や使いどころのイメージが持てる
   

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5. ɹ
   ɹ
   アジェンダ
   ●resultBuilderとは
   
   
   ●仕組みと実装方法
   
   
   ●導入事例の紹介
   
   
   ●まとめ
   

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6. ɹ
   ɹ
   resultBuilderとは
   

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7. ɹ
   ɹ
   複数要素の組み合わせ作業を、
   
   
   命令的ではなく、宣言的に行えるようにする機能
   

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8. ɹ
   ɹ
   → 冗長な実装をシンプルに
   複数要素の組み合わせ作業を、
   
   
   命令的ではなく、宣言的に行えるようにする機能
   

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9. ɹ
   ɹ
   resultBuilderとは何か？
   ● Swift5.4で追加されたAttribute
   
   
   ● 列挙された要素を収集し、結果の値に変換して取得できる
   
   
   ● Swiftで内部DSLを作るための補助機能
   
   
   ● 特定領域で効果を発揮するミニチュア言語を作れる
   

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10. ɹ
    ɹ
    どこで使われてると思いますか？
    
    
    （ここから5秒間、心で念じる or コメント or Tweetする時間）
    

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11. ɹ
    ɹ
    どこで使われている？
    ●ViewBuilder：SwiftUIのレイアウトを記述する時
    
    
    ●RegexComponentBuilder：正規表現を記述する時（NEW!）
    

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12. ɹ
    ɹ
    どこで使われている？
    let word = OneOrMore(.word)
    
    
    let emailPattern = Regex {
    
    
    Capture {
    
    
    ZeroOrMore {
    
    
    word
    
    
    "."
    
    
    }
    
    
    word
    
    
    }
    
    
    "@"
    
    
    Capture {
    
    
    word
    
    
    OneOrMore {
    
    
    "."
    
    
    word
    
    
    }
    
    
    }
    
    
    }
    
    
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    List(album.songs) { song in
    
    
    HStack {
    
    
    Image(album.cover)
    
    
    VStack(alignment: .leading) {
    
    
    Text(song.title)
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    ViewBuilder RegexComponentBuilder
    

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13. ɹ
    ɹ
    let word = OneOrMore(.word)
    
    
    let emailPattern = Regex {
    
    
    Capture {
    
    
    ZeroOrMore {
    
    
    word
    
    
    "."
    
    
    }
    
    
    word
    
    
    }
    
    
    "@"
    
    
    Capture {
    
    
    word
    
    
    OneOrMore {
    
    
    "."
    
    
    word
    
    
    }
    
    
    }
    
    
    }
    
    
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    List(album.songs) { song in
    
    
    HStack {
    
    
    Image(album.cover)
    
    
    VStack(alignment: .leading) {
    
    
    Text(song.title)
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    どこで使われている？
    ViewBuilder RegexComponentBuilder
    

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14. ɹ
    ɹ
    let word = OneOrMore(.word)
    
    
    

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15. ɹ
    ɹ
    どのように表現できる？
    1.値の列挙にカンマが必要ない
    
    
    2.if文やfor文などの制御構文も利用可能
    @ArrayBuilder
    
    
    func someFunction2() ->
    [Int] {
    
    
    1
    
    
    2
    
    
    
    
    if true {
    
    
    3
    
    
    }
    
    
    
    
    for i in (4...6) {
    
    
    i
    
    
    }
    
    
    }
    

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16. ɹ
    ɹ
    何ができる？
    1.値の列挙にカンマが必要ない
    
    
    2.if文やfor文などの制御構文も利用可能
    @ArrayBuilder
    
    
    func someFunction2() ->
    [Int] {
    
    
    1
    
    
    2
    
    
    
    
    if true {
    
    
    3
    
    
    }
    
    
    
    
    for i in (4...6) {
    
    
    i
    
    
    }
    
    
    }
    ಉ݁͡Ռ͕ಘΒΕΔ
    = [1, 2, 3, 4, 5, 6]
    func someFunction1() -> [Int] {
    
    
    var result = [
    
    
    1,
    
    
    2
    
    
    ]
    
    
    
    
    if true {
    
    
    result.append(3)
    
    
    }
    
    
    
    
    for i in (4...6) {
    
    
    result.append(i)
    
    
    }
    
    
    
    
    return result
    
    
    }
    

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17. ɹ
    ɹ
    なぜ必要？
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    List(album.songs) { song in
    
    
    HStack {
    
    
    Image(album.cover)
    
    
    VStack(alignment: .leading) {
    
    
    Text(song.title)
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    

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18. ɹ
    ɹ
    resultBuilderを使わずに同じことを実現する場合
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    List(album.songs) { song in
    
    
    HStack {
    
    
    Image(album.cover)
    
    
    VStack(alignment: .leading) {
    
    
    Text(song.title)
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    var items: [View] = []
    
    
    for song in album.songs {
    
    
    let hStack = HStack(
    
    
    contents: [
    
    
    Image(album.cover),
    
    
    VStack(
    
    
    alignment: .leading,
    
    
    contents [
    
    
    Text(song.title),
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    ]
    
    
    )
    
    
    ]
    
    
    )
    
    
    items.append(hStack)
    
    
    }
    
    
    return List(contents: items)
    
    
    }
    
    
    }
    
    
    ※ ͜ͷίʔυ͸͋͘·ͰΠϝʔδͰ͢
    

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19. ɹ
    ɹ
    もしresultBuilderを使わずに同じことを実現すると
    ● 制御文や変数宣言でコードが肥大化
    
    
    ● 階層構造が複雑で、結果が想像しづらい
    
    
    ● 変更コストが大きい
    struct AlbumDetail: View {
    
    
    var album: Album
    
    
    var body: some View {
    
    
    var items: [View] = []
    
    
    for song in album.songs {
    
    
    let hStack = HStack(
    
    
    contents: [
    
    
    Image(album.cover),
    
    
    VStack(
    
    
    alignment: .leading,
    
    
    contents [
    
    
    Text(song.title),
    
    
    Text(song.artist.name)
    
    
    .foregroundStyle(.secondary)
    
    
    ]
    
    
    )
    
    
    ]
    
    
    )
    
    
    items.append(hStack)
    
    
    }
    
    
    return List(contents: items)
    
    
    }
    
    
    }
    
    
    ※ ͜ͷίʔυ͸͋͘·ͰΠϝʔδͰ͢
    

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20. ɹ
    ɹ
    resultBuilder
    何ができる？　　　　　シンプルな記述で、複数要素の収集と結果値への変換ができる
    
    
    どこで使われている？　SwiftUIやRegexなどで用いられている
    
    
    なぜ必要？　　　　　　可読性・保守性の向上が期待できるため
    

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21. ɹ
    ɹ
    SwiftUI, Regex以外に使い道あるの？
    
    
    

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22. ɹ
    ɹ
    SwiftUI, Regex以外に使い道あるの？
    
    
    ↓
    
    
    カスタムのresultBuilderの作成で
    
    
    実装効率を高められるケースがある
    

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23. ɹ
    ɹ
    例えばこういう時
    let mas = NSMutableAttributedString(string: “")
    
    
    mas.append(NSAttributedString(
    
    
    string: "Hello world",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 24),
    
    
    .foregroundColor: UIColor.red
    
    
    ]
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "\n"
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "with Swift",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 20),
    
    
    .foregroundColor: UIColor.orange
    
    
    ]
    
    
    ))
    
    
    

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24. ɹ
    ɹ
    • 要素指定と関係ない記述が多い
    
    
    • 構造がわかりづらい
    
    
    • 変更による修正量が多い
    例えばこういう時
    let mas = NSMutableAttributedString(string: “")
    
    
    mas.append(NSAttributedString(
    
    
    string: "Hello world",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 24),
    
    
    .foregroundColor: UIColor.red
    
    
    ]
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "\n"
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "with Swift",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 20),
    
    
    .foregroundColor: UIColor.orange
    
    
    ]
    
    
    ))
    
    
    

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25. ɹ
    ɹ
    例えばこういう時
    let mas = NSMutableAttributedString(string: “")
    
    
    mas.append(NSAttributedString(
    
    
    string: "Hello world",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 24),
    
    
    .foregroundColor: UIColor.red
    
    
    ]
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "\n"
    
    
    ))
    
    
    mas.append(NSAttributedString(
    
    
    string: "with Swift",
    
    
    attributes: [
    
    
    .font: UIFont.systemFont(ofSize: 20),
    
    
    .foregroundColor: UIColor.orange
    
    
    ]
    
    
    ))
    
    
    let attributedString = NSAttributedString {
    
    
    AText("Hello world")
    
    
    .font(.systemFont(ofSize: 24))
    
    
    .foregroundColor(.red)
    
    
    LineBreak()
    
    
    AText("with Swift")
    
    
    .font(.systemFont(ofSize: 20))
    
    
    .foregroundColor(.orange)
    
    
    }
    • 要素指定と関係ない記述が多い
    
    
    • 構造がわかりづらい
    
    
    • 変更による修正量が多い
    • 要素指定以外の記述が少ない
    
    
    • 構造がわかりやすい
    
    
    • 変更による修正量が少ない
    // https://github.com/ethanhuang13/NSAttributedStringBuilder
    

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26. ɹ
    ɹ
    awesome-result-builders
    https://github.com/carson-katri/awesome-result-builders
    // Data
    
    
    Data {
    
    
    [UInt8(0)]
    
    
    UInt8(1)
    
    
    Int8(2)
    
    
    "\u{03}"
    
    
    Int16(1284)
    
    
    if dataClause {
    
    
    CustomData()
    
    
    }
    
    
    }
    // Parsing
    
    
    let capture = HTML {
    
    
    TryCapture("#hello") { (element: HTMLElement?) -> String? in
    
    
    return element?.textContent
    
    
    }
    
    
    
    
    Local("#group") {
    
    
    Capture("h1", transform: \.textContent)
    
    
    Capture("h2", transform: \.textContent)
    
    
    }
    
    
    }
    
    
    // Networking
    
    
    Request {
    
    
    Url("https://jsonplaceholder.typicode.com/posts")
    
    
    Method(.post)
    
    
    Header.ContentType(.json)
    
    
    Body(Json([
    
    
    "title": "foo",
    
    
    "body": "bar",
    
    
    "usedId": 1
    
    
    ]).stringified)
    
    
    }
    // GraphQL
    
    
    Operation(.query) {
    
    
    Add(\.country,
    alias: "canada") {
    
    
    Add(\.name)
    
    
    Add(\.continent) {
    
    
    Add(\.name)
    
    
    }
    
    
    }.code("CA")
    
    
    }
    
    
    

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27. ɹ
    ɹ
    仕組みと実装方法
    

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28. ɹ
    ɹ
    作る
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [1, 2, 3]
    

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29. ɹ
    ɹ
    作る
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [1, 2, 3]
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    

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30. ɹ
    ɹ
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    作る
    resultBuilderアノテーションの付与
    

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31. ɹ
    ɹ
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    作る
    buildBlock関数を定義
    

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32. ɹ
    ɹ
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    作る
    引数として受け取れる型 & 返却値の型を指定
    

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33. ɹ
    ɹ
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    作る
    インプット値をアウトプット値に変換
    

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34. ɹ
    ɹ
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [1, 2, 3]
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    使う
    作成したクラス名をアノテーションでfunc, var, etcに付与する
    

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35. ɹ
    ɹ
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [1, 2, 3]
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    使う
    buildBlockの引数の型に対応した値を列挙
    

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36. ɹ
    ɹ
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [1, 2, 3]
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    使う
    指定された返却値の型の値が返される
    

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37. ɹ
    ɹ
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    
    
    someFunction() // [2, 4, 6]
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components.map { $0 * 2 }
    
    
    }
    
    
    }
    使う
    任意の処理を挟むことができる
    

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38. ɹ
    ɹ
    最低限必要な実装はこれだけ、ただし…
    

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39. ɹ
    ɹ
    制御構文への対応
    @ArrayBuilder
    
    
    func function1() -> [Int] {
    
    
    // Closure containing control flow statement cannot be used with result builder 'ArrayBuilder'
    
    
    if true {
    
    
    1
    
    
    }
    
    
    }
    
    
    @ArrayBuilder
    
    
    func function2() -> [Int] {
    
    
    // Closure containing control flow statement cannot be used with result builder 'ArrayBuilder'
    
    
    for i in (2..<10) {
    
    
    i
    
    
    }
    
    
    }
    If,forͳͲͷར༻ʹ͸ɺରԠ͢ΔbuildXXXؔ਺Λ࣮૷͢Δඞཁ͕͋Δ
    

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40. ɹ
    ɹ
    buildXXX関数
    ؔ਺ ݺͼग़͞ΕΔՕॴ
    buildBlock ϒϩοΫ͝ͱ
    buildExpression ࣜ͝ͱ
    buildOptional elseͷͳ͍෼ذ
    buildEither
    elseͷ͋Δ෼ذ
    switchʹΑΔ෼ذ
    buildArray ܁Γฦ͠
    buildFinalResult ݁Ռͷ஋ͷ׬੒
    buildLimitedAvailability #availableʹΑΔ෼ذ
    buildPartialResult ϒϩοΫͷߦ͝ͱ
    ※ ΦʔόʔϩʔυՄೳ
    

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41. ɹ
    ɹ
    buildBlock
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    2
    
    
    3
    
    
    }
    

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42. ɹ
    ɹ
    buildBlock
    func someFunction() -> [Int] {
    
    
    let v0 = 1
    
    
    let v1 = 2
    
    
    let v2 = 3
    
    
    return ArrayBuilder.buildBlock(v0, v1, v2)
    
    
    }
    

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43. ɹ
    ɹ
    buildBlock
    func someFunction() -> [Int] {
    
    
    let v0 = 1
    
    
    let v1 = 2
    
    
    let v2 = 3
    
    
    return ArrayBuilder.buildBlock(v0, v1, v2)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    }
    

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44. ɹ
    ɹ
    分岐への対応
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    if Bool.random() {
    
    
    2
    
    
    3
    
    
    }
    
    
    }
    

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45. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1
    
    
    if Bool.random() {
    
    
    2
    
    
    3
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    

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46. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    

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47. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    ؔ਺ ݺͼग़͞ΕΔՕॴ
    buildOptional elseͷͳ͍෼ذ
    

    View Slide

48. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    

    View Slide

49. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    

    View Slide

50. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    Error!
    

    View Slide

51. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    Int [Int]
    

    View Slide

52. ɹ
    ɹ
    分岐への対応
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    ᶃ v0Λ[Int]ʹม׵ͯ͠ܕ͕ἧ͏Α͏ʹ͢Δ
    ᶄ buildBlockͰ[Int]ͷՄม௕Ҿ਺Λ౉ͤΔΑ͏ʹ͢Δ
    

    View Slide

53. ɹ
    ɹ
    ① v0を[Int]に変換して型が揃うようにする
    func someFunction() -> [Int] {
    
    
    let v0: Int = 1
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0 = 2
    
    
    let v1_1 = 3
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    ᶃ v0Λ[Int]ʹม׵ͯ͠ܕ͕ἧ͏Α͏ʹ͢Δ
    

    View Slide

54. ɹ
    ɹ
    ① v0を[Int]に変換して型が揃うようにする
    func someFunction() -> [Int] {
    
    
    let v0: [Int] = ArrayBuilder.buildExpression(expression: 1)
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0: [Int] = ArrayBuilder.buildExpression(expression: 2)
    
    
    let v1_1: [Int] = ArrayBuilder.buildExpression(expression: 3)
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildExpression(_ expression: Int) -> [Int] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    
    
    ؔ਺ ݺͼग़͞ΕΔՕॴ
    buildExpression ࣜ͝ͱ
    ᶃ v0Λ[Int]ʹม׵ͯ͠ܕ͕ἧ͏Α͏ʹ͢Δ
    

    View Slide

55. ɹ
    ɹ
    ② buildBlockで[Int]の可変長引数を渡せるようにする
    func someFunction() -> [Int] {
    
    
    let v0: [Int] = ArrayBuilder.buildExpression(expression: 1)
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0: [Int] = ArrayBuilder.buildExpression(expression: 2)
    
    
    let v1_1: [Int] = ArrayBuilder.buildExpression(expression: 3)
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildExpression(_ expression: Int) -> [Int] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildBlock(_ components: Int...) -> [Int] {
    
    
    components
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    
    
    ᶄ buildBlockͰ[Int]ͷՄม௕Ҿ਺Λ౉ͤΔΑ͏ʹ͢Δ
    

    View Slide

56. ɹ
    ɹ
    ② buildBlockで[Int]の可変長引数を渡せるようにする
    func someFunction() -> [Int] {
    
    
    let v0: [Int] = ArrayBuilder.buildExpression(expression: 1)
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0: [Int] = ArrayBuilder.buildExpression(expression: 2)
    
    
    let v1_1: [Int] = ArrayBuilder.buildExpression(expression: 3)
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildExpression(_ expression: Int) -> [Int] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildBlock(_ components: [Int]...) -> [Int] {
    
    
    components.flatMap { $0 }
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    
    
    ᶄ buildBlockͰ[Int]ͷՄม௕Ҿ਺Λ౉ͤΔΑ͏ʹ͢Δ
    

    View Slide

57. ɹ
    ɹ
    最終的な実装
    func someFunction() -> [Int] {
    
    
    let v0: [Int] = ArrayBuilder.buildExpression(expression: 1)
    
    
    let v1: [Int]
    
    
    if Bool.random() {
    
    
    let v1_0: [Int] = ArrayBuilder.buildExpression(expression: 2)
    
    
    let v1_1: [Int] = ArrayBuilder.buildExpression(expression: 3)
    
    
    let v1_block: [Int] = ArrayBuilder.buildBlock(v1_0, v1_1)
    
    
    v1 = ArrayBuilder.buildOptional(v1_block)
    
    
    } else {
    
    
    v1 = ArrayBuilder.buildOptional(nil)
    
    
    }
    
    
    return ArrayBuilder.buildBlock(v0, v1)
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildExpression(_ expression: Int) -> [Int] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildBlock(_ components: [Int]...) -> [Int] {
    
    
    components.flatMap { $0 }
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    

    View Slide

58. ɹ
    ɹ
    最終的な実装
    @ArrayBuilder
    
    
    func someFunction() -> [Int] {
    
    
    1
    
    
    if Bool.random() {
    
    
    2
    
    
    3
    
    
    }
    
    
    }
    @resultBuilder struct ArrayBuilder {
    
    
    static func buildExpression(_ expression: Int) -> [Int] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildBlock(_ components: [Int]...) -> [Int] {
    
    
    components.flatMap { $0 }
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [Int]?) -> [Int] {
    
    
    component ?? []
    
    
    }
    
    
    }
    

    View Slide

59. ɹ
    ɹ
    その他制御構文への対応
    for i in (1...3) {
    
    
    i
    
    
    }
    var v0: [Int] = []
    
    
    for i in (1...3) {
    
    
    // ...
    
    
    v0.append(i_block)
    
    
    }
    
    
    let v0_array = ArrayBuilder.buildArray(v0)
    if Bool.random() {
    
    
    1
    
    
    } else {
    
    
    2
    
    
    }
    if Bool.random() {
    
    
    // ...
    
    
    v0 = ArrayBuilder.buildEither(first: v1_block)
    
    
    } else {
    
    
    // ...
    
    
    v0 = ArrayBuilder.buildEither(second: v2_block)
    
    
    }
    WWDC2021: Write a DSL in Swift using result builders
    

    View Slide

60. ɹ
    ɹ
    導入事例の紹介
    

    View Slide

61. ɹ
    ɹ
    STORES レジ
    ● 2021.06リリースしたiPadアプリ
    
    
    ● 店舗運営を支援するPOSシステムを提供
    
    
    ● フルSwiftUI
    SwiftUI+GraphQLͰϓϩμΫτͷܧଓతͳഁյʹཱͪ޲͔͏ʢ iOSDC2021ʣ
    

    View Slide

62. ɹ
    ɹ
    レシート印刷
    

    View Slide

63. ɹ
    ɹ
    レシート印刷の流れ
    ϨΠΞ΢τ༻ಠࣗXML ը૾σʔλ
    ϓϦϯλʔ΁ૹ৴
    ม׵
    

    View Slide

64. ɹ
    ɹ
    ϨΠΞ΢τ༻ಠࣗXML ը૾σʔλ
    ϓϦϯλʔ΁ૹ৴
    ม׵
    独自ルールに基づいたXML文字列の生成
    
    
    
    
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    
    
    
    ϔομʔϝοηʔδ
    
    
    
    
    
    ΞΠςϜ໊1
    
    
    2000ԁ
    
    
    2000ԁ
    
    
    
    
    
    
    
    
    ※ 社内の別アプリでの仕組みを、STORES レジ用に移植
    

    View Slide

65. ɹ
    ɹ
    独自ルールに基づいたXML文字列の生成
    
    
    
    
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    
    
    
    ϔομʔϝοηʔδ
    
    
    
    
    
    ΞΠςϜ໊1
    
    
    2000ԁ
    
    
    2000ԁ
    
    
    
    
    
    
    
    
    var xml = ""
    
    
    if let src = receiptSetting.logoImageURL?.absoluteString {
    
    
    xml += "”
    
    
    }
    
    
    xml += """
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    """
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    let label = "(item.price) x \(item.quantity)"
    
    
    xml += """
    
    
    \(item.name)
    
    
    \(item.totalPrice)
    
    
    “""
    
    
    } else {
    
    
    xml += ""
    
    
    xml += "\(item.totalPrice)"
    
    
    xml += ""
    
    
    }
    
    
    }
    
    
    // ~ লུ ~
    
    
    xml += ""
    
    
    return xml
    
    
    

    View Slide

66. ɹ
    ɹ
    XMLベタ書きの問題
    1.型安全でなく、想定外の文字があると壊れる
    
    
    2.冗長な記述が多く、レイアウト構造と非対応で見通しが悪い
    
    
    3.変更があった場合、改修コストが高い
    
    
    4.指定可能な値の把握がしづらい
    var xml = ""
    
    
    if let src = receiptSetting.logoImageURL?.absoluteString {
    
    
    xml += "”
    
    
    }
    
    
    xml += """
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    """
    

    View Slide

67. ɹ
    ɹ
    var xml = ""
    
    
    if let src = receiptSetting.logoImageURL?.absoluteString {
    
    
    xml += "”
    
    
    }
    
    
    xml += """
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    """
    XMLベタ書きの問題
    ཁ͸ɺݸʑͷXMLཁૉΛऩूͯ͠ɺจࣈྻΛੜ੒͍ͯ͠Δ͚ͩ
    → resultBuilderͰͷཁૉͷऩूʹద͍ͯ͠Δ
    

    View Slide

68. ɹ
    ɹ
    実装の概要
    protocol ReceiptElement {
    
    
    var body: String { get }
    
    
    }
    各要素を同一視するためのProtocolを定義
    

    View Slide

69. ɹ
    ɹ
    実装の概要
    protocol ReceiptElement {
    
    
    var body: String { get }
    
    
    }
    struct Text: ReceiptElement {
    
    
    var body: String {
    
    
    “some text"
    
    
    }
    
    
    }
    struct Image: ReceiptElement {
    
    
    var body: String {
    
    
    “”
    
    
    }
    
    
    }
    各要素を同一視するためのProtocolを定義
    利用できるXML要素を準拠させる
    ※ આ໌ͷͨΊ؆ུԽͨ͠ίʔυΛࡌ͍ͤͯ·͢
    

    View Slide

70. ɹ
    ɹ
    実装の概要
    @resultBuilder struct ReceiptBuilder {
    
    
    static func buildBlock(_ components: ReceiptElement...) -> [ReceiptElement] {
    
    
    components
    
    
    }
    
    
    
    
    static func buildBlock(_ components: [ReceiptElement]...) -> [ReceiptElement] {
    
    
    components.flatMap { $0 }
    
    
    }
    
    
    
    
    static func buildExpression(_ expression: ReceiptElement) -> [ReceiptElement] {
    
    
    [expression]
    
    
    }
    
    
    
    
    static func buildExpression(_ expression: [ReceiptElement]) -> [ReceiptElement] {
    
    
    expression
    
    
    }
    
    
    
    
    static func buildEither(first component: [ReceiptElement]) -> [ReceiptElement] {
    
    
    component
    
    
    }
    
    
    
    
    static func buildEither(second component: [ReceiptElement]) -> [ReceiptElement] {
    
    
    component
    
    
    }
    
    
    
    
    static func buildOptional(_ component: [ReceiptElement]?) -> [ReceiptElement] {
    
    
    component ?? []
    
    
    }
    
    
    
    
    static func buildArray(_ components: [[ReceiptElement]]) -> [ReceiptElement] {
    
    
    components.flatMap { $0 }
    
    
    }
    
    
    }
    ReceiptElementをresultBuilderで収集
    

    View Slide

71. ɹ
    ɹ
    実装の概要
    struct Receipt {
    
    
    let buildElements: () -> [ReceiptElement]
    
    
    
    
    init(@ReceiptBuilder buildElements: @escaping () -> [ReceiptElement]) {
    
    
    self.buildElements = buildElements
    
    
    }
    
    
    
    
    var xml: String {
    
    
    let elements = buildElements()
    
    
    return Tag(.receipt).build(VStack(elements).body)
    
    
    }
    
    
    
    
    func image(width: CGFloat) async throws -> UIImage {
    
    
    let builder = ReceiptImageBuilder(width: width)
    
    
    return try await builder.build(xml: xml)
    
    
    }
    
    
    }
    
    
    

    View Slide

72. ɹ
    ɹ
    実装の概要
    struct Receipt {
    
    
    let buildElements: () -> [ReceiptElement]
    
    
    
    
    init(@ReceiptBuilder buildElements: @escaping () -> [ReceiptElement]) {
    
    
    self.buildElements = buildElements
    
    
    }
    
    
    
    
    var xml: String {
    
    
    let elements = buildElements()
    
    
    return Tag(.receipt).build(VStack(elements).body)
    
    
    }
    
    
    
    
    func image(width: CGFloat) async throws -> UIImage {
    
    
    let builder = ReceiptImageBuilder(width: width)
    
    
    return try await builder.build(xml: xml)
    
    
    }
    
    
    }
    
    
    ①
    1.resultBuilderをイニシャライザで受け取る
    

    View Slide

73. ɹ
    ɹ
    実装の概要
    struct Receipt {
    
    
    let buildElements: () -> [ReceiptElement]
    
    
    
    
    init(@ReceiptBuilder buildElements: @escaping () -> [ReceiptElement]) {
    
    
    self.buildElements = buildElements
    
    
    }
    
    
    
    
    var xml: String {
    
    
    let elements = buildElements()
    
    
    return Tag(.receipt).build(VStack(elements).body)
    
    
    }
    
    
    
    
    func image(width: CGFloat) async throws -> UIImage {
    
    
    let builder = ReceiptImageBuilder(width: width)
    
    
    return try await builder.build(xml: xml)
    
    
    }
    
    
    }
    
    
    ①
    ②
    1.resultBuilderをイニシャライザで受け取る
    
    
    2.受け取ったresultBuilderでReceiptElementの配列を収集
    

    View Slide

74. ɹ
    ɹ
    実装の概要
    struct Receipt {
    
    
    let buildElements: () -> [ReceiptElement]
    
    
    
    
    init(@ReceiptBuilder buildElements: @escaping () -> [ReceiptElement]) {
    
    
    self.buildElements = buildElements
    
    
    }
    
    
    
    
    var xml: String {
    
    
    let elements = buildElements()
    
    
    return Tag(.receipt).build(VStack(elements).body)
    
    
    }
    
    
    
    
    func image(width: CGFloat) async throws -> UIImage {
    
    
    let builder = ReceiptImageBuilder(width: width)
    
    
    return try await builder.build(xml: xml)
    
    
    }
    
    
    }
    
    
    ①
    ②
    ③
    1.resultBuilderをイニシャライザで受け取る
    
    
    2.受け取ったresultBuilderでReceiptElementの配列を収集
    
    
    3.収集した要素をXML文字列に変換
    

    View Slide

75. ɹ
    ɹ
    実装の概要
    1.resultBuilderをイニシャライザで受け取る
    
    
    2.受け取ったresultBuilderでReceiptElementの配列を収集
    
    
    3.収集した要素をXML文字列に変換
    
    
    4.XML文字列を画像に変換
    struct Receipt {
    
    
    let buildElements: () -> [ReceiptElement]
    
    
    
    
    init(@ReceiptBuilder buildElements: @escaping () -> [ReceiptElement]) {
    
    
    self.buildElements = buildElements
    
    
    }
    
    
    
    
    var xml: String {
    
    
    let elements = buildElements()
    
    
    return Tag(.receipt).build(VStack(elements).body)
    
    
    }
    
    
    
    
    func image(width: CGFloat) async throws -> UIImage {
    
    
    let builder = ReceiptImageBuilder(width: width)
    
    
    return try await builder.build(xml: xml)
    
    
    }
    
    
    }
    
    
    ①
    ②
    ③
    ④
    

    View Slide

76. ɹ
    ɹ
    Before: XMLベタ書き
    var xml = ""
    
    
    if let src = receiptSetting.logoImageURL?.absoluteString {
    
    
    xml += "”
    
    
    }
    
    
    xml += """
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    """
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    let label = "(item.price) x \(item.quantity)"
    
    
    xml += """
    
    
    \(item.name)
    
    
    \(item.totalPrice)
    
    
    “""
    
    
    } else {
    
    
    xml += ""
    
    
    xml += "\(item.totalPrice)"
    
    
    xml += ""
    
    
    }
    
    
    }
    
    
    // ~ লུ ~
    
    
    xml += ""
    
    
    return xml
    
    
    

    View Slide

77. ɹ
    ɹ
    Before: XMLベタ書き
    Receipt {
    
    
    if let src = receiptSetting.logoImageURL {
    
    
    Image(src: src)
    
    
    .maxHeight(96)
    
    
    }
    
    
    
    
    Title(“͝ར༻໌ࡉ")
    
    
    Divider()
    
    
    
    
    VStack(spacing: 2) {
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    Text(item.name)
    
    
    .truncated()
    
    
    
    
    LabelText(label: "\(item.price) x \(item.quantity)",
    
    
    content: item.totalPrice)
    
    
    } else {
    
    
    LabelText(label: item.name,
    
    
    content: item.totalPrice)
    
    
    .truncated()
    
    
    }
    
    
    }
    
    
    }
    
    
    }
    
    
    

    View Slide

78. ɹ
    ɹ
    Before: XMLベタ書き
    let receiptImage = try await Receipt {
    
    
    if let src = receiptSetting.logoImageURL {
    
    
    Image(src: src)
    
    
    .maxHeight(96)
    
    
    }
    
    
    
    
    Title(“͝ར༻໌ࡉ")
    
    
    Divider()
    
    
    
    
    VStack(spacing: 2) {
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    Text(item.name)
    
    
    .truncated()
    
    
    
    
    LabelText(label: "\(item.price) x \(item.quantity)",
    
    
    content: item.totalPrice)
    
    
    } else {
    
    
    LabelText(label: item.name,
    
    
    content: item.totalPrice)
    
    
    .truncated()
    
    
    }
    
    
    }
    
    
    }
    
    
    }.image(width: 240)
    
    
    

    View Slide

79. ɹ
    ɹ
    let receiptImage = try await Receipt {
    
    
    if let src = receiptSetting.logoImageURL {
    
    
    Image(src: src)
    
    
    .maxHeight(96)
    
    
    }
    
    
    
    
    Title(“͝ར༻໌ࡉ")
    
    
    Divider()
    
    
    
    
    VStack(spacing: 2) {
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    Text(item.name)
    
    
    .truncated()
    
    
    
    
    LabelText(label: "\(item.price) x \(item.quantity)",
    
    
    content: item.totalPrice)
    
    
    } else {
    
    
    LabelText(label: item.name,
    
    
    content: item.totalPrice)
    
    
    .truncated()
    
    
    }
    
    
    }
    
    
    }
    
    
    }.image(width: 240)
    
    
    var xml = ""
    
    
    if let src = receiptSetting.logoImageURL?.absoluteString {
    
    
    xml += "”
    
    
    }
    
    
    xml += """
    
    
    ͝ར༻໌ࡉ
    
    
    
    
    
    """
    
    
    for item in items {
    
    
    if item.quantity >= 2 {
    
    
    let label = "(item.price) x \(item.quantity)"
    
    
    xml += """
    
    
    \(item.name)
    
    
    \(item.totalPrice)
    
    
    “""
    
    
    } else {
    
    
    xml += ""
    
    
    xml += "\(item.totalPrice)"
    
    
    xml += ""
    
    
    }
    
    
    }
    
    
    // ~ লུ ~
    
    
    xml += ""
    
    
    return xml
    
    
    After: resultBuilder利用
    

    View Slide

80. ɹ
    ɹ
    resultBuilderの活用による効果
    1. 型安全でなく、想定外の文字があると壊れる
    
    
    2. シンプルな表現で、レイアウト構造と対応して見通しが良い
    
    
    3. 変更する際に、コンパイラの助けを借りられる
    
    
    4. 指定可能な値をコード補完で把握できる
    XMLベタ書き resultBuilderを活用
    苦しい実装 楽しい実装
    

    View Slide

81. ɹ
    ɹ
    まとめ
    

    View Slide

82. ɹ
    ɹ
    ● ボイラープレートを削減し、冗長なコードを圧倒的にシンプル化できる
    
    
    ● コードの見通しが良くなり、結果が予想しやすくなる
    
    
    ● 宣言的な記述が主になるため、変更が容易になる
    resultBuilderの利点
    

    View Slide

83. ɹ
    ɹ
    ● DSLは利用者に学習を求めることになる
    
    
    ● 無闇な導入は過度な抽象化をもたらし、逆にコストが高くなる恐れもある
    
    
    ● 機能の利用自体が目的とならないよう、使い所の見極めは必要
    注意点
    

    View Slide

84. ɹ
    ɹ
    ● 特定の結果を生成するために、複数要素を組み合わせる場合
    
    
    ● ユースケースに応じて、様々な組み合わせが生まれる場合
    
    
    ● 要素の追加や削除などが行われやすい場合
    resultBuilderの効果的な使い所
    

    View Slide

85. ɹ
    ɹ
    ありがとうございました！
    ࠾༻΋΍ͬͯΔΑʂ
    

    View Slide