如何使用ObservableObject更新UIViewRepresentable [英] How to update UIViewRepresentable with ObservableObject

问题描述

我试图学习与SwiftUI结合，并且正在努力使用ObservableObject(以前是BindableObject)更新我的视图(从UIKit).问题是，很明显，一旦@Published对象发送更改通知，方法updateUIView就不会触发.

I'm trying to learn Combine with SwiftUI and I'm struggling how to update my view (from UIKit) with ObservableObject (previously BindableObject). The issue is that, obviously, method updateUIView will not fire once the @Published object sends the notification it was changed.

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)
    }
}

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

How to bind that locationCoordinates array to the view in such a way, that a new point is in fact added each time it refreshes?

推荐答案

要确保您的ObservedObject不会被多次创建(您只需要一个副本)，可以将其放在UIViewRepresentable之外:

To make sure your ObservedObject does not get created multiple times (you only want one copy of it), you can put it outside your UIViewRepresentable:

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)
    }
}

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