如何用 ObservableObject 更新 UIViewRepresentable

Question

我正在尝试学习结合 SwiftUI，我正在努力如何使用 ObservableObject（以前是 BindableObject）更新我的视图（从 UIKit）。问题是，很明显，一旦 @Published 对象发送它已更改的通知，方法 updateUIView 将不会触发。

class DataSource: ObservableObject {
    @Published var locationCoordinates = [CLLocationCoordinate2D]()
    var value: Int = 0

    init() {
        Timer.scheduledTimer(withTimeInterval: 3, repeats: true) { timer in
            self.value += 1
            self.locationCoordinates.append(CLLocationCoordinate2D(latitude: 52, longitude: 16+0.1*Double(self.value)))
        }
    }
}

struct MyView: UIViewRepresentable {
    @ObservedObject var dataSource = DataSource()

    func makeUIView(context: Context) -> MKMapView {
        MKMapView(frame: .zero)
    }

    func updateUIView(_ view: MKMapView, context: Context) {
        let newestCoordinate = dataSource.locationCoordinates.last ?? CLLocationCoordinate2D(latitude: 52, longitude: 16)
        let annotation = MKPointAnnotation()
        annotation.coordinate = newestCoordinate
        annotation.title = "Test #\(dataSource.value)"
        view.addAnnotation(annotation)
    }
}

如何以这种方式将 locationCoordinates 数组绑定到视图，实际上每次刷新时都会添加一个新点？

Answer 1

为了确保您的 ObservedObject 不会被多次创建（您只想要一份副本），您可以将它放在 UIViewRepresentable 之外：

import SwiftUI
import MapKit

struct ContentView: View {
    @ObservedObject var dataSource = DataSource()

    var body: some View {
        MyView(locationCoordinates: dataSource.locationCoordinates, value: dataSource.value)
    }
}
class DataSource: ObservableObject {
    @Published var locationCoordinates = [CLLocationCoordinate2D]()
    var value: Int = 0

    init() {
        Timer.scheduledTimer(withTimeInterval: 3, repeats: true) { timer in
            self.value += 1
            self.locationCoordinates.append(CLLocationCoordinate2D(latitude: 52, longitude: 16+0.1*Double(self.value)))
        }
    }
}

struct MyView: UIViewRepresentable {
    var locationCoordinates: [CLLocationCoordinate2D]
    var value: Int

    func makeUIView(context: Context) -> MKMapView {
        MKMapView(frame: .zero)
    }

    func updateUIView(_ view: MKMapView, context: Context) {
        print("I am being called!")
        let newestCoordinate = locationCoordinates.last ?? CLLocationCoordinate2D(latitude: 52, longitude: 16)
        let annotation = MKPointAnnotation()
        annotation.coordinate = newestCoordinate
        annotation.title = "Test #\(value)"
        view.addAnnotation(annotation)
    }
}

Answer 2

这个解决方案对我有用，但使用了 EnvironmentObject https://gist.github.com/svanimpe/152e6539cd371a9ae0cfee42b374d7c4

Answer 3

我将为任何使用组合表示的 UI/NS 视图提供通用解决方案。我的方法有性能优势。

创建了一个 Observable 对象并用 @Published 包装器
通过视图中的updateView方法注入Observed对象可使用您将在步骤 3 中创建的方法表示
将视图模型作为参数对所需视图进行子类化。创建一个 addViewModel 方法并使用合并运营商/订阅者并将它们添加到可取消。

注意 - 适用于环境对象。

    struct swiftUIView : View {
      @EnvironmentObject var env : yourViewModel
      ...
      ...
          UIViewRep(wm : env)
     }

    struct UIViewRep : UIViewRepresentable {

     var wm : yourViewModel
     
     func makeUIView {
      let yv = yourView()
      yv.addViewModel(wm)
      return yv
      }}

    class yourView : UIView {
     var viewModel : yourViewModel?
     var cancellable = Set<AnyCancellable>()
     ...
     ...
     func addViewModel( _ wm : yourViewModel) {
     self.viewModel = wm

      self.viewModel?.desiredProperty
          .sink(receiveValue: { [unowned self] w in
        print("Make changes with ", w)
       }).store(in: &cancellable)
      }
    }

如何用 ObservableObject 更新 UIViewRepresentable

How to update UIViewRepresentable with ObservableObject

uikit

mapkit

swift

swiftui

combine