SwiftUI：保存MapKit注释数据以传递到另一个视图

问题描述

我正在努力保存MapKit注释数据（例如名称，地址，坐标等），然后将其传递回具有链接到地图视图的视图。我可以使用didSelect选择注释并将所需的数据打印到终端，但是我不知道如何将其传递回去。我一直在尝试使用Observedobject，但出现一条错误消息：属性'self.contentData'未在隐式生成的super.init调用中初始化。

import SwiftUI
import MapKit

//MARK:- COORDINATOR
class Coordinator: NSObject,MKMapViewDelegate {
    
    //@Observedobject var contentData: ContentData  // << deleted based on answer
    
    var control: MapUIView
    var contentData: ContentData  // << added based on answer
    
    init(_ control: MapUIView) {
        self.control = control
        self.contentData = control.contentData // << added based on answer
    }
    
    func mapView(_ mapView: MKMapView,didAdd views: [MKAnnotationView]) {
        if let annotationView = views.first {
            if let annotation = annotationView.annotation {
                if annotation is MKUserLocation {
                    let region = MKCoordinateRegion(center: annotation.coordinate,latitudinalMeters: 8000,longitudinalMeters: 8000)
                    mapView.setRegion(region,animated: true)
                }
            }
        }
    }
    
    func selectAnnotation(_ annotation: MKAnnotation,animated: Bool) {
        
    }
    
    func mapView(_ mapView: MKMapView,didSelect view: MKAnnotationView) {
        if mapView.selectedAnnotations.count > 0 {
            if let selectedPinName = mapView.selectedAnnotations[0].title {
                print("\(selectedPinName!)")
            }
        }
        let region = MKCoordinateRegion(center: view.annotation!.coordinate,span: mapView.region.span)
        mapView.setRegion(region,animated: true)
        contentData.selectedLocationName = (mapView.selectedAnnotations[0].title as? String)!
    }

}

//MARK:- LOCATION MANAGER
class LocationManager: NSObject,ObservableObject {
    private let locationManager = CLLocationManager()
    @Published var location: CLLocation? = nil
    override init() {
        super.init()
        self.locationManager.delegate = self
        self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
        self.locationManager.distanceFilter = kCLheadingFilterNone
        self.locationManager.requestWhenInUseAuthorization()
        self.locationManager.startUpdatingLocation()
    }
}

extension LocationManager: CLLocationManagerDelegate {
    func locationManager(_ manager: CLLocationManager,didChangeAuthorization status: CLAuthorizationStatus) {
        print(status)
    }
    func locationManager(_ manager: CLLocationManager,didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else {
            return
        }
        self.location = location
    }
}

//MARK:- LANDMARK ANNOTATION
final class LandmarkAnnotation: NSObject,MKAnnotation {
    let title: String?
    let subtitle: String?
    let coordinate: CLLocationCoordinate2D
    
    init(landmark: Landmark) {
        self.title = landmark.name
        self.subtitle = landmark.title
        self.coordinate = landmark.coordinate
    }
}

//MARK:- LANDMARK
struct Landmark {
    let placemark: MKPlacemark
    var id: UUID {
        return UUID()
    }
    var name: String {
        self.placemark.name ?? ""
    }
    var title: String {
        self.placemark.title ?? ""
    }
    var coordinate: CLLocationCoordinate2D {
        self.placemark.coordinate
    }
}

//MARK:- VIEW
struct MapView: View {
    @Observedobject var locationManager = LocationManager()
    @State private var landmarks: [Landmark] = [Landmark]()
    @State private var search: String = ""
    @State private var tapped: Bool = false
    @State private var showCancelButton: Bool = false
    
    @Observedobject var contentData: ContentData

    private func getNearByLandmarks() {
        let request = MKLocalSearch.Request()
        request.naturalLanguageQuery = search
        let search = MKLocalSearch(request: request)
        search.start { (response,error) in
            if let response = response {
                let mapItems = response.mapItems
                self.landmarks = mapItems.map {
                    Landmark(placemark: $0.placemark)
                }
            }
        }
    }
    
    var body: some View {
        ZStack(alignment: .top) {
            MapUIView(contentData: contentData,landmarks: landmarks)
            HStack {
                HStack {
                    Image(systemName: "magnifyingglass")
                    TextField("Search",text: $search,onEditingChanged: { _ in
                        self.showCancelButton = true
                        self.getNearByLandmarks()
                    }).foregroundColor(.primary)
                    Button(action: {
                        self.search = ""
                    }) {
                        Image(systemName: "xmark.circle.fill").opacity(search == "" ? 0 : 1)
                    }
                }
                .padding(EdgeInsets(top: 8,leading: 6,bottom: 8,trailing: 6))
                .foregroundColor(.secondary)
                .background(Color(.secondarySystemBackground))
                .cornerRadius(10.0)
            }
            .padding(EdgeInsets(top: 10,leading: 0,bottom: 1,trailing: 0))
            .padding(.horizontal)
        }
    }
}

//MARK:- MAPUIVIEW
struct MapUIView: UIViewRepresentable {
    @Observedobject var contentData: ContentData
    let landmarks: [Landmark]
    func makeUIView(context: Context) -> MKMapView {
        let map = MKMapView()
        map.showsUserLocation = true
        map.delegate = context.coordinator
        return map
    }
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    func updateUIView(_ uiView: MKMapView,context: UIViewRepresentableContext<MapUIView>) {
        updateAnnotations(from: uiView)
    }
    func updateAnnotations(from mapView: MKMapView) {
        mapView.removeAnnotations(mapView.annotations)
        let annotations = self.landmarks.map(LandmarkAnnotation.init)
        mapView.addAnnotations(annotations)
    }
}

struct MapView_Previews: PreviewProvider {
    static var previews: some View {
        MapView(contentData: ContentData())
    }
}

调用地图视图：

NavigationLink(destination: MapView(contentData: contentData).edgesIgnoringSafeArea(.bottom),tag: 1,selection: $tag)

任何帮助将不胜感激。提前非常感谢。

编辑----------------------

在实施建议的更改之前和之后添加了注释行为的屏幕快照，以允许将注释数据与ObservableObject一起传递回先前的swiftui视图。

解决方法

这是固定的部分

class Coordinator: NSObject,MKMapViewDelegate {
    
    var contentData: ContentData  // << here !!
    var control: MapUIView
    
    init(_ control: MapUIView) {
        self.control = control
        self.contentData = control.contentData   // << here !!
    }

    // ... other code
}

注意：@ObservedObject设计为可在SwiftUI视图中使用，而在类中则不需要