SwiftUIでCompletionを使おう

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@State var isAuthorized: Bool = false
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// 中略
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ZStack {
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    NavigationLink(destination: DestinationView(), isActive: $isAuthorized, label: { EmptyView() })
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    PasscodeLock($isAuthorized)
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}

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@State var isPresented: Bool = false
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Button(action: { isPresented.toggle() }, label: { Text("AUTHORIZE") })
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DestinationView()
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    .passcodeLock(isPresented: $isPresented) {
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        PasscodeLockView() { completion in
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            switch completion {
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                case .finished:
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                    break
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                case .failure(let error):
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                    print(error)
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            }
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        }
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    }

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@State var isPresented: Bool = false
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ZStack {
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    NavigationLink(destination: DestinationView(), isActive: $isPresented, label: { EmptyView() })
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    PasscodeLockView() { completion in
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        switch completion {
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            case .finished:
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                isPresented.toggle()
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            case .failure(let error):
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                print(error)
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        }
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    }
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}

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.webAuthenticationSession(isPresented: $startingWebAuthenticationSession) {
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    WebAuthenticationSession(
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        url: URL(string: "https://github.com/login/oauth/authorize")!,
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        callbackURLScheme: "github"
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    ) { callbackURL, error in
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        print(callbackURL, error)
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    }
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    .prefersEphemeralWebBrowserSession(false)
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}

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public init(
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    url: URL,
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    callbackURLScheme: String?,
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    completionHandler: @escaping (_ callbackURL: URL?, _ error: Error?) -> Void
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) {
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    self.url = url
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    self.callbackURLScheme = callbackURLScheme
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    self.completionHandler = completionHandler
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}

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public typealias CompletionHandler = ASWebAuthenticationSession.CompletionHandler // <- CompletionHandler
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/// A completion handler for the web authentication session.
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public typealias OnCompletion = (_ result: Result<URL, Error>) -> Void
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// MARK: Representation Properties
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let url: URL
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let callbackURLScheme: String?
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let completionHandler: CompletionHandler // <- CompletionHandler

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let completionHandler = ASWebAuthenticationSession.CompletionHandler

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// Enter
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PasscodeEnterView(passcode: passcode, withBiometrics: true) { result in
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    // 成功したかどうかのフラグresultによって処理を変える
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}
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PasscodeSetView() { result in
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    // resultに新たなパスコードが入っている
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}
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PasscodeChangeView(passcode: passcode) { result in
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    // 成功したかどうかのフラグresultによって処理を変える
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}

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// Enter
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PasscodeView(state: .enter, passcode: passcode, withBiometrics: true) { result in
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    // 成功したかどうかのフラグresultによって処理を変える
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}
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// Set
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PasscodeView(state: .set) { result in
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    // 成功したかどうかのフラグresultによって処理を変える
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}
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// Change
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PasscodeView(state: .change, passcode: passcode) { result in
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    // 成功したかどうかのフラグresultによって処理を変える
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}

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import SwiftUI
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struct ContentView: View {
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    // 完了ハンドラを決定する
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    typealias CompletionHandler = (Result<Bool, Error>) -> Void
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    let completionHandler: CompletionHandler
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    // パスコードは5にしておく
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    private var passcode: Int = 5
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    init(completionHandler: @escaping CompletionHandler) {
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        self.completionHandler = completionHandler
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    }
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    var body: some View {
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        GeometryReader { geometry in
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            LazyVGrid(columns: Array(repeating: .init(.flexible(minimum: 60, maximum: 80), spacing: 0), count: 3), alignment: .center, spacing: 10, pinnedViews: []) {
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                ForEach(Range(1...9)) { number in
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                    Button(action: { addSign(sender: number)}, label: { Text("\(number)").frame(width: 60, height: 60, alignment: .center) })
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                        .overlay(Circle().stroke(Color.blue, lineWidth: 1))
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                }
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                .buttonStyle(CircleButtonStyle())
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                Button(action: { biometricsAuth() }, label: { Image(systemName: "touchid").resizable().frame(width: 40, height: 40, alignment: .center) })
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                Button(action: { addSign(sender: 0) }, label: { Text("0").frame(width: 60, height: 60, alignment: .center) })
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                    .buttonStyle(CircleButtonStyle())
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                Button(action: {}, label: { Text("Delete").frame(width: 60, height: 60, alignment: .center) })
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            }
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            .position(x: geometry.size.width / 2, y: geometry.size.height / 2)
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        }
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        .edgesIgnoringSafeArea(.all)
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        .background(Color.white)
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    }
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    func addSign(sender: Int) {
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        // ボタンを押したときの処理
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        if sender == passcode {
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            // 一致していればSuccess(True)を返す
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            completionHandler(.success(true))
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        } else {
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            // 一致していなければSuccess(False)を返す
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            completionHandler(.success(false))
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        }
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    }
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}
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// ボタンをかっこよくするためだけのコード
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struct CircleButtonStyle: ButtonStyle {
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    func makeBody(configuration: Configuration) -> some View {
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        configuration.label
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            .foregroundColor(configuration.isPressed ? Color.white : Color.blue)
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            .overlay(Circle().stroke(Color.blue, lineWidth: 1))
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            .contentShape(Circle()
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            .background(Circle().foregroundColor(configuration.isPressed ? Color.blue : Color.clear))
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    }
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}

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public typealias CompletionHandler = ASWebAuthenticationSession.CompletionHandler // <- CompletionHandler
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/// A completion handler for the web authentication session.

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public typealias CompletionHandler = (URL?, Error?) -> Void