Month: May 2022

async / awaitの組み合わせで非同期処理を行う

ContentView.swift

func getWho() async -> String {
    await Task.sleep(5 * 1000 * 1000 * 1000)
    return "山本さん"
}

func getMessage() async -> String {
    await Task.sleep(3 * 1000 * 1000 * 1000)
    return "ハロー"
}

class StopWatch: ObservableObject {
    
    @Published var elapsedTime: Double = 0.0
    private var timer = Timer()
    
    func start() {
        guard !timer.isValid else { return }
        self.elapsedTime = 0.0
        timer = Timer.scheduledTimer(withTimeInterval: 0.01, repeats: true) {
            _ in
            self.elapsedTime += 0.01
        }
    }
    
    func stop() {
        timer.invalidate()
    }
}

struct ContentView: View {
    
    @State var message:String = ""
    @ObservedObject var watch = StopWatch()
    
    var body: some View {
        VStack {
            Button(action: {
                Task {
                    watch.start()
                    message = "_ _ _"
                    
                    async let who = getWho()
                    async let msg = getMessage()
                    message = await who + "," + msg + " ! "
                    watch.stop()
                }
            }) {
                Label("async TEST", systemImage: "testtube.2")
                    .background(
                        Capsule()
                            .stroke(lineWidth: 1)
                            .frame(width: 180, height: 40)
                    )
            }.padding(30)
            Text("\(message)").font(.title2)
            let milliSeconds = Int((watch.elapsedTime) * 100)%100
            let seconds = Int(watch.elapsedTime)
            Text("\(seconds).\(milliSeconds)").padding()
            Spacer()
        }
    }
}

OK, もう一声

複数の画像をダウンロードできたものから表示
AsyncImage, placeholder, List, LazyVGrid, NavigationView, NavigationLink

ContentView.swift

struct Photo: Identifiable {
    var id: URL{url}
    var url: URL
}

class PhotoSource {
    var photos: [Photo] = []
    init() {
        photos = makePhotos()
    }
}

extension PhotoSource {
    func makePhotos() -> [Photo] {
        let path = "https://oshige.xsrv.jp/samples/photos/"
        let photoNames: [String] = [
            "IMG_1159.jpg", "IMG_1326.jpg", "IMG_1384.jpg", "IMG_1475.jpg",
            "IMG_1476.jpg", "IMG_1478.jpg", "IMG_1635.jpg", "IMG_1643.jpg",
            "IMG_1739.jpg", "IMG_1840.jpg", "IMG_1889.jpg", "IMG_2233.jpg",
            "IMG_2325.jpg", "IMG_2406.jpg", "IMG_2408.jpg", "IMG_4008.jpg"
        ]
        
        var photos: [Photo] = []
        for name in photoNames {
            photos.append(Photo(url: URL(string: path + name)!))
        }
        return photos
    }
}

struct ContentView: View {
    
    private var myPhotoSource = PhotoSource()
    
    var body: some View {
        NavigationView {
            List(myPhotoSource.photos) {
                photo in
                
                AsyncImage(url: photo.url) {
                    image in
                    
                    image.resizable()
                        .aspectRatio(contentMode: .fit)
                } placeholder: {
                    Color.orange
                        .overlay(Image(systemName: "photo").scaleEffect(2.0))
                }
                .mask(RoundedRectangle(cornerRadius: 16))
                .frame(height: 160)
            }
            .navigationTitle("お気に入り")
        }
    }
}

なるほど、非同期というとJSって感じだが、Swiftでもあるのね。