sink() 在 combine swift 中不被调用

Question

I have LocationManager class that works well. This is part of LocationManager class.

  var headingDegree = PassthroughSubject<Double, Never>()

  func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
    headingDegree.send(-newHeading.magneticHeading)
  }

headingDegree is the value I want to send to my ViewModel. I debugged it to make sure it has correct values, and it does.

So, in my view model,

class CompassViewViewModel: ObservableObject {
 @Published var degree: Double = 0.0
 @State var cancellable = Set<AnyCancellable>()

 func update() {
    LocationManager.shared.headingDegree.sink {
      self.degree = $0
    }
    .store(in: &cancellable)
  }

I sinked my headingDegree . This is the part that brings my problems. If I put breakpoints in update() function, self.degree = $0 is never called.

This is how my View looks like.

struct CompassView: View {
  @ObservedObject var viewModel: CompassViewViewModel

  init(viewModel: CompassViewViewModel) {
    self.viewModel = viewModel
  }

 var body: some View {
    ZStack {
      Text("aa")
        .font(.footnote)
    }
      .onAppear {
        self.viewModel.update()
    }
  }
}

Could you tell me why my sink() is not called?

Answer 1

我将@State var cancellable = Set<AnyCancellable>()更改为private var cancellable = Set<AnyCancellable>()并且效果很好。

Answer 2

Update

in swiftUI1, viewDidLoad in UIHostingcontroller isn't called.

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when using combine, with UIKit, subscribing (Sink) in viewDidload, didn't work, instead, subscribe in viewDidAppear