Swift async/await關(guān)鍵字

在日常項(xiàng)目開發(fā)中，一般耗時(shí)的操作我們不可能全部讓主線程去做完，會(huì)導(dǎo)致app的卡頓。我們一般都是異步執(zhí)行的。

以圖片渲染為例子。

閉包

從前我們經(jīng)常是異步下載了圖片，然后閉包為回調(diào)觸發(fā)使用。

異步下載圖片閉包回調(diào)

    private func blockGetImage(completionHandler: @escaping(Data) -> Void) {
        
        DispatchQueue.global().async {
            let url : URL = URL(string: "http://i8-static.jjwxc.net/tmp/backend/authorspace/s1/28/27087/2708639/20220518224228.jpg")!
            let data : Data = try! Data(contentsOf: url)
            DispatchQueue.main.async {
                completionHandler(data)
            }
        }
    }}

閉包使用

SwiftUI

    var body: some View {
        VStack
        {
            Image(uiImage: UIImage(data: data) ?? UIImage())
                .resizable()
        }
        .onAppear {
            print("name = \(self)")
            blockGetImage {
                data = $0
            }
        }
        .navigationTitle("async和await")
    }

Swift

    override func viewDidLoad() {
        super.viewDidLoad()
        self.img = UIImageView(frame: CGRect(x: 0, y: 100, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height - 100))
        self.view.addSubview(self.img)
        
        blockGetImage {
            self.img.image = UIImage(data: $0)
        }
        
   }

async/await

async是異步請(qǐng)求
await是將async異步轉(zhuǎn)為同步

    // async方式得到圖片的Data
    private func asyncGetImage() async -> Data {
        do {
            let (d, _) = try await URLSession.shared.data(for: URLRequest(url: URL(string: "http://i8-static.jjwxc.net/tmp/backend/authorspace/s1/28/27087/2708639/20220518224228.jpg")!))
            return d
        } catch {
            return Data()
        }
    }

SwiftUI使用

    var body: some View {
        VStack
        {
            Image(uiImage: UIImage(data: data) ?? UIImage())
                .resizable()
        }
        .onAppear {
            print("name = \(self)")
        }
        .task { 
            data = await asyncGetImage()
        }
        .navigationTitle("async和await")
    }

Swift使用

    override func viewDidLoad() {
        super.viewDidLoad()
        self.img = UIImageView(frame: CGRect(x: 0, y: 100, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height - 100))
        self.view.addSubview(self.img)
        
        Task {
            self.img.image = await UIImage(data: asyncGetImage())
        }
    }

Github地址

懶得打的可以直接打開項(xiàng)目查看 Github地址 https://github.com/HahnLoving/iOS_Study