使用 MVVM-Pattern 处理 SwiftUI 和 CoreLocation

Question

我正在尝试使用MVVM-Pattern实现SwiftUI和CoreLocation。我作为助手LocationManager工作正常。但是我如何更改LocationViewModel的属性？我在LocationViewModel年实现了对LocationManager@ObservedObject。这是我的问题。

我没有实现他们动态更改的属性的想法。我的位置视图中没有任何更改。通过按下按钮，任何工作都可以正常工作一次。但是LocationViewModel必须在每次更改LocationManager时更改那里的属性。

总之，我想显示当前用户的位置。

// Location Manager as Helper
import Foundation
import CoreLocation
class LocationManager: NSObject, ObservableObject {
let locationManager = CLLocationManager()
let geoCoder = CLGeocoder()
@Published var location: CLLocation?
@Published var placemark: CLPlacemark?
override init() {
super.init()
self.locationManager.delegate = self
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()
}
func geoCode(with location: CLLocation) {
geoCoder.reverseGeocodeLocation(location) { (placemark, error) in
if error != nil {
print(error!.localizedDescription)
} else {
self.placemark = placemark?.first
}
}
}
}
extension LocationManager: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let location = locations.first else { return }
DispatchQueue.main.async {
self.location = location
self.geoCode(with: location)
}
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
// TODO
}
}

// Location Model
import Foundation
import CoreLocation
struct Location {
var location: CLLocation = CLLocation()
var placemark: CLPlacemark = CLPlacemark()
}

// Location View Model
import SwiftUI
import CoreLocation
class LocationViewModel: ObservableObject {
@ObservedObject var locationManager: LocationManager = LocationManager()
@Published var location: Location
init() {
self.location = Location()
}
}

// Location View
import SwiftUI
struct LocationView: View {
@ObservedObject var locationViewModel: LocationViewModel = LocationViewModel()
var body: some View {
VStack(alignment: .leading) {
Text("Latitude: (self.locationViewModel.location.location.coordinate.latitude.description)")
Text("Longitude: (self.locationViewModel.location.location.coordinate.longitude.description)")
}
}
}
struct LocationView_Previews: PreviewProvider {
static var previews: some View {
LocationView()
}
}

更新

现在，我已经设置了我的地图视图。

但是我如何接收LocationManager的数据？didUpdateLocations方法在LocationManager中起作用。

我试图做的所有事情都出错了。我想根据当前用户位置在我的MapView上设置区域。在UIKit中，它非常简单，但在SwiftUI中，它很奇怪。

// Map View
import SwiftUI
import MapKit
struct MapView: UIViewRepresentable {
@ObservedObject var locationManager: LocationManager = LocationManager()
class Coordinator: NSObject, MKMapViewDelegate {
var parent: MapView
init(_ control: MapView) {
self.parent = control
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIView(context: Context) -> MKMapView {
let mapView = MKMapView(frame: .zero)
mapView.delegate = context.coordinator
return mapView
}
func updateUIView(_ mapView: MKMapView, context: Context) {
mapView.showsUserLocation = true
}
}
struct MapView_Previews: PreviewProvider {
static var previews: some View {
MapView()
}
}

Answer 1

SwiftUI 2

在这种情况下使用代替StateObject

struct LocationView: View {
@StateObject var locationManager: LocationManager = LocationManager()
...

迅捷 1

实际上LocationViewModel在这里是多余的。由于您的LocationManager是ObservableObject因此您可以直接在视图中使用它，如下所示：

struct LocationView: View {
@ObservedObject var locationManager: LocationManager = LocationManager()
var body: some View {
VStack(alignment: .leading) {
Text("Latitude: (locationManager.location.coordinate.latitude.description)")
Text("Longitude: (locationManager.location.coordinate.longitude.description)")
}
}
}