swift - 如何使用 ObservableObject 更新 UIViewRepresentable

Question

我正在尝试学习与 SwiftUI 结合，我正在努力如何使用 ObservableObject 更新我的 View (来自 UIKit) (以前的 BindableObject )。显然，问题是方法 updateUIView不会触发 @Published对象发送它已更改的通知。

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)
    }
}

如何绑定(bind) locationCoordinates以这样的方式将数组添加到 View 中，实际上每次刷新时都会添加一个新点？

Answer 1

确保您的 ObservedObject不会被多次创建(你只想要一份)，你可以把它放在你的 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)
    }
}