swiftui 无法更改接收器中的@State 值

Question

我现在正在学习swiftui，我是Whosebug的新手，我发现了一个问题，这是我的代码。我想更改 sink 中的@State nopubName，但是它不起作用，打印总是“Nimar”，我不知道为什么

struct ContentView: View {
   
    @State var nopubName: String = "Nimar"
    private var cancellable: AnyCancellable?
    
    var stringSubject = PassthroughSubject<String, Never>()

    init() {
        cancellable = stringSubject.sink(receiveValue: handleValue(_:))
    }
    
    func handleValue(_ value: String) {
         print("handleValue: '\(value)'")
        self.nopubName = value
        print("in sink "+nopubName)
     }
    
    var body: some View {
        VStack {
            Text(self.nopubName)
                .font(.title).bold()
                .foregroundColor(.red)
            Spacer()
 
            Button("sink"){
                stringSubject.send("World")
                print(nopubName)

            }
        }
    }
}

Answer 1

You should only access a state property from inside the view’s body, or from methods called by it.

https://developer.apple.com/documentation/swiftui/state

您可以在 ObservableObject 中使用该功能并更新 @Published 以保持 UI 更新

https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app

Answer 2

不需要使用Combine，如果在View范围内，可以直接改变@State变量的值

struct ContentView: View {
    @State var nopubName: String = "Nimar"
    var body: some View {
        VStack {
            Text(self.nopubName)
                .font(.title).bold()
                .foregroundColor(.red)
            Spacer()

            Button("sink"){
                nopubName = "World"
            }
        }
    }
}

swiftui 无法更改接收器中的@State 值

swiftui cannot change @State value in sink

state

sink

combine